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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Life Science
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Journal DOI :
Korean Society of Life Science
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Volume & Issues
Volume 24, Issue 12 - Dec 2014
Volume 24, Issue 11 - Nov 2014
Volume 24, Issue 10 - Oct 2014
Volume 24, Issue 9 - Sep 2014
Volume 24, Issue 8 - Aug 2014
Volume 24, Issue 7 - Jul 2014
Volume 24, Issue 6 - Jun 2014
Volume 24, Issue 5 - May 2014
Volume 24, Issue 4 - Apr 2014
Volume 24, Issue 3 - Mar 2014
Volume 24, Issue 2 - Feb 2014
Volume 24, Issue 1 - Jan 2014
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Spatial Distribution Pattern of the Populations of Camellia japonica in Busan
Kang, Man Ki ; Huh, Man Kyu ;
Journal of Life Science, volume 24, issue 8, 2014, Pages 813~819
DOI : 10.5352/JLS.2014.24.8.813
The spatial distribution of geographical distances at five natural populations of Camellia japonica in Busan, Korea was studied. The four plots (Mollundae, Gadeok-do, Du-do, and Jwiseum) of C. japonica were uniformly distributed in the forest community and only one plot (Amnam-dong) was aggregately distributed in the forest community. Morisita index is related to the patchiness index showed that the plot
had an overly steep slope when the area was larger than
, which indicated that the degree of aggregation increased significantly with increasing quadrat sizes, while the patchiness indices did not change from the plot
. The spatial structure was quantified by Moran's I, a coefficient of spatial autocorrelation. Ten of the significant values (76.9%) were positive, indicating similarity among individuals in the first 4 distance classes (80 m), i.e., pairs of individuals with dissimilarity characteristics can separate by more than 100 m.
Parkin Interacts with the PDZ Domain of Multi-PDZ Domain Protein MUPP1
Jang, Won Hee ; Jeong, Young Joo ; Choi, Sun Hee ; Lee, Won Hee ; Kim, Mooseong ; Kim, Sang-Jin ; Urm, Sang-Hwa ; Moon, Il Soo ; Seog, Dae-Hyun ;
Journal of Life Science, volume 24, issue 8, 2014, Pages 820~826
DOI : 10.5352/JLS.2014.24.8.820
The localization to specific subcellular sites and the regulation of cell surface receptors and channels are crucial for proper functioning. Postsynaptic density-95/Disks large/Zonula occludens-1 (PDZ)-domain is involved in recognition of and interaction between various proteins, by which the localization and the regulation are mediated. Multi-PDZ domain protein 1 (MUPP1) contains 13 PDZ domains. MUPP1 serves a scaffolding function for structure proteins and signaling proteins, but the mechanism how MUPP1 is stabilized and signalized has not yet been elucidated. We used the yeast two-hybrid system to identify proteins that interact with PDZ domains of MUPP1. We found an interaction between MUPP1 and Parkin. Parkin is an E3 ubiquitin ligase. Loss-of-function mutations of Parkin gene are known to cause an autosomal recessive juvenile parkinsonism. Parkin bound to the
PDZ domain, but not to other PDZ domains of MUPP1. The C-terminal end of Parkin has a type II PDZ-association motif, which was essential for the interaction with MUPP1 in the yeast two-hybrid assay. When co-expressed in HEK-293T cells, Parkin co-localized with MUPP1. When co-expressed with ubiquitin in HEK-293T cells, MUPP1 has been strongly ubiquitinated by Parkin. These findings collectively suggest that MUPP1 is a novel substrate of Parkin and its function or stability could be modulated by Parkin-mediated ubiquitination.
Antiobesity Effect of Citrus Peel Extract Fermented with Aspergillus oryzae
Jeon, Hyun Joo ; Yu, Sun Nyoung ; Kim, Sang Hun ; Park, Seul Ki ; Choi, Hyeun Deok ; Kim, Kwang Yeon ; Lee, Sun Yi ; Chun, Sung Sik ; Ahn, Soon Cheo ;
Journal of Life Science, volume 24, issue 8, 2014, Pages 827~836
DOI : 10.5352/JLS.2014.24.8.827
There is a rising trend in obesity due to various factors, including changes in eating habits, lack of exercise, and genetic and psychological factors. Citrus peel has been reported to prevent obesity via antioxidative, antihypertensive, and LDL cholesterol-lowering effects. This study investigated the effects of citrus peel extract fermented with or without Aspergillus oryzae in a mouse model of diet-induced obesity. The animals were divided into four groups: a high-fat diet group (HFD), a normal fat diet (NFD) group, a citrus peel extract (CP) group, and a citrus peel extract fermented with A. oryzae (CPA) group. The citrus peel extract improved lipid metabolism and weight loss in the high-fat diet-induced obese mouse model. As expected, the body weight was higher in the HFD group compared with the NFD, CP, and CPA groups. However, the concentrations of total cholesterol (TG) and triglyceride (TC) in the serum and liver of the CP and CPA groups were lower than in the HFD group. There were no significant differences in the HDL cholesterol concentration among the groups. Taken together, our results suggest that extract of citrus peel biotransformed with A. oryzae had more antiobesity activity than citrus peel not transformed by A. oryzae through the fermentation of metabolites.
The Effect of Brunfelsia grandiflora Ethanol Extract on the Induction of Autophagy in Human Lung Fibroblasts
Nam, Hyang ; Kim, Moon-Moo ;
Journal of Life Science, volume 24, issue 8, 2014, Pages 837~842
DOI : 10.5352/JLS.2014.24.8.837
The purpose of this study was to investigate the effect of Brunfelsia grandiflora ethanol extract (BGEE) on the induction of autophagy via regulation of SIRT1 expression and p53 activation in a human lung fibroblast cell line, IMR 90. BGEE at a concentration of
or more exhibited a cytotoxic effect on IMR 90 cells. For the first time, this study showed that BGEE induces autophagy in normal human lung fibroblasts. BGEE also increased the expression level of beclin-1 at
or less and Atg7 at
, both of which are known to be involved in the induction of autophagy. In addition, BGEE modulated the expression of other proteins related to autophagy in normal human lung fibroblasts. The expression levels of p53 and p-p53, an active form of p53, were decreased in the presence of BGEE at a noncytotoxic concentration. In contrast, the expression level of SIRT1 was increased in human lung fibroblasts treated with BGEE at a noncytotoxic concentration. Moreover, SA-
-Gal staining, an aging marker, was reduced in the normal human lung fibroblasts treated with BGEE. These findings suggest that BGEE promotes the induction of autophagy and antiaging through the modulation of p53 and SIRT1 in human lung fibroblasts.
Anti-inflammatory Effects of Extracts and Their Solvent Fractions of Rice Wine Lees
Park, Mi-Jeong ; Kang, Hyung-Taek ; Kim, Mi-Sun ; Shin, Woo-Chang ; Sohn, Ho-Yong ; Kim, Jong-Sik ;
Journal of Life Science, volume 24, issue 8, 2014, Pages 843~850
DOI : 10.5352/JLS.2014.24.8.843
In the current study, we prepared eighty-five different kinds of solvent fractions of rice wine lees and nuruk extracts and investigated their effects on cell viability and nitric oxide (NO) production in mouse RAW 264.7 cells. Among the treated solvent fractions, only three solvent fractions (KSD-E1-3, KSD-E2-3 and KSD-E4-3) significantly decreased NO production in LPS-activated RAW 264.7 cells without affecting cell viability. And, they also reduced the expression of pro-inflammatory genes such as COX-2, TNF-alpha and iNOS. To understand the molecular mechanisms involved in the inhibition of inflammation in (KSD-E4-3)-treated RAW 264.7 cells, we carried out oligo DNA microarray analysis using Agilent Mouse microarray. To confirm microarray data, 6 genes (IL-1F6, iNOS, IL-10, Fabp4, IL-1RN and CSF2) were selected and performed RT-PCR and quantitative real-time PCR analysis with gene specific primers. The results of RT-PCR and real-time PCR agreed with microarray data. Overall, our results suggest that rice wine lees can be a novel resource for the development of foods and drugs which possess anti-inflammatory activity.
Medicinal Herb Extracts Attenuate 1-Chloro-2,4dinitrobenzene-induced Development of Atopic Dermatitis-like Skin Lesions
Lee, Moon Hee ; Han, Min Ho ; Yoon, Jung Jeh ; Song, Myung Kyu ; Kim, Min Ju ; Hong, Su Hyun ; Choi, Byung Tae ; Kim, Byung Woo ; Hwang, Hye Jin ; Choi, Yung Hyun ;
Journal of Life Science, volume 24, issue 8, 2014, Pages 851~859
DOI : 10.5352/JLS.2014.24.8.851
The present study was designed to investigate whether ethanol extracts of Sophora flavescens (GS), Glycyrrhiza uralensis (GC), Dictamnus dasycarpus (BSP), and their mixtures (GGB-1, -2, -3, and -4) inhibit 1-chloro-2,4-dinitrobenzene (DNCB)-induced atopic dermatitis (AD) in a mouse model. DNCB was topically applied on the dorsal surface of Balb/c mice to induce AD-like skin lesions. The pathological phenotypes of AD, such as erythema, ear thickness, edema, scabs, and discharge, were significantly decreased in the GGB (DNCB + GS:GC:BSP = 3:1:1 mixture)-1-treated groups compared with the other treated groups. The weight of the spleen in immune organs was significantly decreased in the GGB-1-treated groups, whereas the weight of the liver in a control group was similar to that of the groups treated with the samples. Furthermore, toluidine blue staining analysis, a method used to specifically identify mast cells, showed that master cell infiltration into the dermis of the GGB-1-treated group was significantly decreased. The immunoglobulin E concentration was lower in the GGB-1-treated group. In addition, the levels of inflammatory cytokines (interferon-
, interleukin-1, 4, 5, 6, and 13,
, and tumor necrosis factor-
) were also significantly reduced in the GGB-1-treated group. Taken together, these results suggest that a mixture of GS, GC, and BSP in a proportion of 3:1:1 (GGB-1) may contribute to the relief of AD symptoms and may be considered an excellent candidate for an AD therapeutic drug.
Purification of Two Novel Antimicrobial Peptides from Pyloric Caeca of the Starfish Asterina pectinifera
Go, Hye-Jin ; Bae, Yun Jung ; Park, Nam Gyu ;
Journal of Life Science, volume 24, issue 8, 2014, Pages 860~864
DOI : 10.5352/JLS.2014.24.8.860
PAP-1, a novel antimicrobial peptide isolated from pyloric caeca extract of the starfish Asterina pectinifera was purified and characterized. First, the acidified pyloric caeca extract was put through Sep-Pak C18 solid phase extraction cartridge using a stepwise gradient. Among the eluents, RM 60 (retained materials at 60% methanol) showed good antimicrobial activity against Bacillus subtilis and Escherichia coli D31 and was purified in C18 reversed-phase and ion-exchange high-performance liquid chromatography columns. The purification steps yielded two novel peptides showing strong antimicrobial activities. These peptides were named pyloric caeca A. pectinifera peptide 1 and 2 (PAP-1 and PAP-2). For the characterization of the purified peptides, the molecular weights and amino acid sequences were determined by MALDI-TOF MS and Edman degradation. The molecular weights of PAP-1 and PAP-2 were about 2951.54 Da and 2980.15 Da respectively. The amino acid sequences of PAP-1 and PAP-2 were partially determined: AIQNAGES and AIQNAAES, respectively. PAP-2 is an isoform of PAP-1, differing merely by a single residue at position 6 (glycine or alanine). The comparison of the N-terminal amino acid sequences and molecular weights of the peptides with those of other known antimicrobial peptides revealed that PAP-1 and PAP-2 have no homology with any known peptides. These findings suggest that PAP-1 and PAP-2 play a significant role in the innate defense system of starfish pyloric caeca.
Evaluation of in-vitro Antithrombosis Activity of Lees of Korean Traditional Wine
Kim, Mi-Sun ; Lee, Ye-Seul ; Kim, Jong Sik ; Shin, Woo-Chang ; Sohn, Ho-Yong ;
Journal of Life Science, volume 24, issue 8, 2014, Pages 865~872
DOI : 10.5352/JLS.2014.24.8.865
In this study, ethanol and hot water extracts of lees from Korean traditional wine (J-B, J-S, J-Y, J-H, and J-W) were prepared, and their effects on blood coagulation, platelet aggregation, and hemolysis of human red blood cells (hRBCs) were investigated to develop functional food ingredients from lees. The pH and brix of the lees ranged from 3.90 to 4.29 and 5.0 to
, respectively, and there was a huge difference in the water and ethanol content among the lees. The nuruk and additives used affected the color and physicochemical properties of lees. The J-W takju made from only rice and traditional nuruk, which has
brix and 1.8% of alcohol, has potential as functional food ingredient. With regard to the extraction yields of lees, higher yields were obtained from J-H, which contains different medicinal plants, in ethanol, followed by J-W, J-B, J-S, and J-Y. Higher extraction yields of lees were obtained from J-S in hot water, followed by J-B, J-W, J-H, and J-Y, respectively. The ethanol extract of J-H and the hot water extract of J-Y had the highest contents of total polyphenol and total flavonoids among the lees extracts. The 10 lees extracts did not show hemolysis activity against hRBCs up to 5 mg/ml. In an anticoagulation activity assay, the ethanol extracts of three yakju lees (J-B, J-S, and J-Y) and the hot water extract of J-W inhibited thrombin activity, whereas the hot water extract of J-B, J-S, and J-H inhibited blood coagulation factors. In an antiplatelet aggregation activity assay, only the J-W takju lees showed significant inhibition activity. Our results suggest that lees from traditional wine had high potential as a novel antithrombosis agent.
Identification of a Neolignan Glycoside from the Pine Tree, Pinus densiflora Showed Antithrombotic Activity
Seo, Min-Jeong ; Kang, Byoung-Won ; Jeong, Yong-Kee ;
Journal of Life Science, volume 24, issue 8, 2014, Pages 873~879
DOI : 10.5352/JLS.2014.24.8.873
The constituents from the needles of the pine tree, Pinus densiflora, were purified and investigated for antithrombotic activity. The needles were initially extracted three times with 70% ethanol, and the extract was sequentially fractionated with chloroform and n-butanol. The aqueous layer formed after n-butanol fractionation was subjected to purification by medium pressure and high pressure liquid chromatography. The two neolignans, 2, 3-dihydro-7-hydroxyl-3-hydroxymethyl-2-(4'-hydroxyl -3-methoxyphenyl)-5-benzofuranpropanol-3-O-
-rhamnopyranoside (a neolignan glycoside) and 2, 3-dihyro-3-hydroxymethyl-7-methoxy-2-(4'-hydroxyphenyl-3'-methoxy)-5-benxofuran propanol 4'-O-
) were identified by
NMR spectra. The effect of the purified compounds, the neolignan glycoside and icariside
on thrombin inhibition were investigated by measuring thrombin clotting time in plasma. As a result, the clotting of the neolignan glycoside was delayed four times compared to that of icariside
. In addition, an analysis of the inhibition effect by changing the concentration showed that the clotting time was delayed in accordance with an increase in the concentration of the neolignan glycoside. Furthermore, we examined the interaction of thrombin and fibrinogen to clarify the action mechanism. As a result, the delay of clotting time in the response of thrombin and pure fibrinogen may indicate that neolignan glycosides inhibit the thrombin action in a direct manner, leading to the suppression of fibrin generation.
The Antibacterial Activity Against Fish Pathogen of Paenibacillus sp. MK-11 Isolated from Jeju Coast
Kim, Min-Sun ; Park, So-Hyun ; Kim, Dong-Hwi ; Heo, Moon-Soo ;
Journal of Life Science, volume 24, issue 8, 2014, Pages 880~886
DOI : 10.5352/JLS.2014.24.8.880
In this study, we isolate and identify bacteria from seawater collected from Jeju coast, to evaluate the antimicrobial activity against the fish pathogenic bacteria. 14 bacterial strains were isolated and identified using physiological, biochemical and molecular tools. Antibacterial activity of all the 14 isolates were screened against four major fish pathogens namely, two Gram-positive: Streptococcus iniae, Streptococcus parauberis and two Gram-negative: Vibrio anguillarum, Edwardsiella tarda. Results revealed that among the 14 isolates, MK-11 was found to have antibacterial activity against S. iniae, S. parauberis, V. anguillarum Particularly, S. iniae was susceptibility with the MIC value of
. The biochemical and physio-chemical results reveal that MK-11 had the sugar-alcohol disassemble ability of the D-sorbitol and D-mannitol. Also the utilization of the yeast extract, sorbitol and di-potassium phosphate were noted to be high. The optimum culture condition such as pH and temperature was recorded as pH 6.0,
and along with 1% NaCl which differs from the previous reports particularly in nutrient resolutions. As results of the analysis of 16S rDNA sequences, MK-11 show the high similarity with Paenibacillus polymyxa, P. jamilae, P. brasilensis 99.78%, 99.43%, 99.39%, repectively. Hence, in the present study, the isolated Paemibacillus sp. MK-11 from Jeju seawater possesses the antibacterial activity against fish pathogens and it could be used as a new antibiotic agents against the gram positive fish pathogens.
Development of Microbial Augmentation for the Treatment of Recalcitrant Industrial Wastewater Containing Chlorinated Organic Compounds
Lee, Hyun Don ; Im, Seong Won ; Suh, Hyun-Hyo ;
Journal of Life Science, volume 24, issue 8, 2014, Pages 887~894
DOI : 10.5352/JLS.2014.24.8.887
The screening of the microorganisms degrading chlorinated organic compounds such as PCP (pentachlorophenol) and TCE (trichloroethylene) was conducted with soil and industrial wastewater contaminated with various chlorinated organic compounds. Isolates (GP5, GP19) capable of degrading PCP and isolates (GA6, GA15) capable of degrading TCE were identified as Acetobactor sp., Pseudomonas sp., Arthrobacer sp., Xanthomonas sp. and named Acetobacter sp. GP5, Pseudomonas sp. GP19, Arthrobacer sp. GA6 and Xanthomoas sp. GA15, respectively. The microbial augmentation, OC17 formulated with the mixture of bacteria including isolates (4 strains) degrading chlorinated organic compounds and isolates (Acinetobacter sp. KN11, Neisseria sp. GN13) degrading aromatic hydrocarbons. Characteristics of microbial augmentation OC-17 showed cell mass of
, bulk density of
and water content of 26.8%. In the experiment with an artificial wastewater containing PCP (500 mg/l), degradation efficiency of the microbial augmentation OC17 was 87% during incubation of 65 hours. The degradation efficiency of TCE (300 uM) by microbial augmentation OC17 was 90% during incubation of 50 hours. In a continuous culture experiment, analysis of the biodegradation of organic compounds by microbial augmentation OC17 in industry wastewater containing chlorinated hydrocarbons showed that the removal rate of COD was 91% during incubation of 10 days. These results indicate that it is possible to apply the microbial augmentation OC17 to industrial wastewaters containing chlorinated organic compounds.
Correlation of Gene Expression between Adiponectin and Glucose Transporter 4 in Mouse Adipose Tissue
Lee, Yong-Ho ;
Journal of Life Science, volume 24, issue 8, 2014, Pages 895~902
DOI : 10.5352/JLS.2014.24.8.895
Adiponectin has been known to improve insulin sensitivity and elicit glucose uptake via increased glucose transporter 4 (GLUT4) translocation. In the current study, mRNA expression levels of adiponectin and GLUT4 were measured in subcutaneous adipose tissue from C57BL/6 mice fed normal (ND) or high-fat diet (HFD) until 16, 26, 36, 47, or 77 weeks of age starting from 6 weeks of age. Expression levels were also measured in mice with calorie restriction (CR) and in thiazolidinedione (TZD) treated mice. Using quantitative real-time PCR, we demonstrated that GLUT4 expression in adipose tissue significantly decreased in HFD mice groups and increased in CR (p<0.05) and TZD (p=0.007) groups while there was no difference in adiponectin mRNA expression levels between experimental and control groups. General linear regression models were used to assess the association of gene expression levels between adiponectin and GLUT4 and to determine whether adiponectin affects GLUT4 transcription. mRNA expression levels of adiponectin and GLUT4 are significantly associated each other in mice fed a ND (p<0.0001) or HFD (p<0.0001), in groups separated into each age and diet, and CR group (p=0.002), but not in TZD group (p=0.73). These results demonstrated that gene expression of adiponectin and GLUT4 is strongly associated, suggesting that there is a common regulatory mechanism for adiponectin and GLUT4 gene expression and/or adiponectin has a direct role in GLUT4 gene expression in adipose tissue.
Antiproliferative and Apoptotic Effects of Sasa quelpaertensis Nakai in Human Cancer Cells
Kim, Ji Hye ; Kim, Min Young ;
Journal of Life Science, volume 24, issue 8, 2014, Pages 903~909
DOI : 10.5352/JLS.2014.24.8.903
Plants are an invaluable source of potential new anti-cancer drugs. Sasa quelpaertensis Nakai (Korean name, Jeju-Joritdae) is one of these plants with medical value, which is a bamboo grass widely distributed in Mt. Halla on Jeju Island, Korea. Here, we investigated the apoptotic effects of S. quelpaertensis leaf extracts in six human cancer cell lines (A549, MCF-7, HepG-2, Hela, HCT116 and A375). MTT assay signified the antiproliferative nature of S. quelpaertensis extracts against all tested cancer cells: S. quelpaertensis displayed slight cytotoxicity against A549, MCF-7 and HepG-2 cells, whereas it was exclusively cytotoxic to Hela, HCT116 and A375 cells. Apoptotic cells were evaluated using PI staining of DNA fragmentation by flow cytometry (sub-G1 peak). PI staining indicated increasing accumulation of Hela, HCT116 and A375 cells at sub-G1 phase. Further events like generation of nitric oxide (
) were accompanied in the S. quelpaertensis Nakai-induced apoptosis. Augmented
generation resulted in the DNA fragmentation of Hela, HCT116 and A375 cells by treatment with S. quelpaertensis leaf extracts. These results suggest that S. quelpaertensis may be a potential natural resource for treating cancer cell. To identify the exact mechanisms of molecular mechanism of S. quelpaertensis induced apoptosis awaits further investigation.
PCR Technique for Determining Jeju Black Cattle, Hanwoo and Imported Beef
Kim, Chan-Su ; Ko, Jung-Moon ; Cha, Hyeon-Cheol ; Park, Joong Kook ; Jeong, Joon ;
Journal of Life Science, volume 24, issue 8, 2014, Pages 910~914
DOI : 10.5352/JLS.2014.24.8.910
For the identification of the Jeju black cattle, Hanwoo and imported beef, we performed a multiplex polymerase chain reaction (PCR) associated with microsatellite (MS) and melanocortin 1 receptor (MC1R) gene. The MC1R gene plays an important role in regulation of the melanin synthesis within mammalian melanocytes. MC1R encoded by extension (E) locus was almost fixed with recessive red e allele in the Hanwoo. We estimated that the specific genotypes (
) of MC1R gene were characteristic genotypes of Jeju black cattle. But the PCR products resulted from using the MC1R gene derived primers only are not sufficient to identify Jeju black cattle from other relatives. We performed two times of successive multiplex PCR to provide a more accurate result for the identification of Jeju black cattle. The results suggest that two types of successive multiplex PCR methods using MC1R gene and Microsatellite derived primer set will be more useful to identification of Jeju black cattle, Hanwoo and imported beef.
Non-ribosomal Ribosome Assembly Factors in Escherichia coli
Choi, Eunsil ; Hwang, Jihwan ;
Journal of Life Science, volume 24, issue 8, 2014, Pages 915~926
DOI : 10.5352/JLS.2014.24.8.915
The ribosome is a protein synthesizing machinery and a ribonucleoprotein complex that consists of three ribosomal RNAs (23S, 16S and 5S) and 54 ribosomal proteins in bacteria. In the course of ribosome assembly, ribosomal proteins (r-protein) and rRNAs are modified, the r-proteins bind to rRNAs to form ribonucleoprotein complexes which are folded into mature ribosomal subunits. In this process, a number of non-ribosomal trans-acting factors organize the assembly process of the components. Those factors include GTP- and ATP-binding proteins, rRNA and r-protein modification enzymes, chaperones, and RNA helicases. During ribosome biogenesis, they participate in the modifications of ribosomal proteins and RNAs, and the assemblies of ribosomal proteins with rRNAs. Ribosomes can be assembled from a discrete set of components in vitro, and it is notable that in vivo ribosome assembly is much faster than in vitro ribosome assembly. This suggests that non-ribosomal ribosome assembly factors help to overcome several kinetic traps in ribosome biogenesis process. In spite of accumulation of genetic, structural, and biochemical data, not only the entire procedure of bacterial ribosome synthesis but also most of roles of ribosome assembly factors remain elusive. Here, we review ribosome assembly factors involved in the ribosome maturation of Escherichia coli, and summarize the contributions of several ribosome assembly factors which associate with 50S and 30S ribosomal subunits, respectively.