Pif1 subfamily helicase is conserved from yeast to humans with a lot of cellular functions. In order to elucidate the function of human PIF1 helicase from biochemical level, we cloned human PIF1 gene by PCR from HeLa cell cDNA library. We co-transformed a pMStRNA1 plasmid encoding rare tRNA codons and a plasmid encoding molecular chaperon to greatly enhance the overexpression of human PIF1 protein. Finally we purified full-length PIF1 helicase by column chromatograph carried out at 4 degrees C using fast protein liquid chromatograph (FPLC) system. The human PIF1 protein was purified in enough quantity for detailed biochemical analysis. Biochemical assay showed that PIF1 had ATPase activity and helicase activity. The purification and biochemical properties analysis of human PIF1 helicase will allow us to understand how, at the molecular and mechanistic level, this conserved helicase operates in the cell.
DNA Helicases ; biosynthesis ; genetics ; metabolism ; HeLa Cells ; Humans ; RNA, Transfer ; genetics ; Recombinant Proteins ; biosynthesis ; genetics ; metabolism

Chromosomal Proteins, Non-Histone ; chemistry ; genetics ; metabolism ; HeLa Cells ; Histones ; chemistry ; genetics ; metabolism ; Humans ; Protein Domains

OBJECTIVE: To investigate the molecular mechanism in stable cell strains expressing Mini-hF9 gene with nonsense mutation. METHODS: Mini-hF9 gene and its nonsense mutants were transfected into HeLa cells independently, and stable cell strains were obtained after G418 resistance screening and monoclonal transformation. The altered splicing and protein expression of mRNA in Mini-hF9 gene in stable cell strains were detected by using RT-PCR and Western blot. RESULTS: The wild type and nonsense mutated human coagulation factor IX stable cell strains were constructed successfully, which were named HeLa-F9-WT, HeLa-F9-M1 and HeLa-F9-M2. Only normal splicing Norm was detected in the wild-type cell strain HeLa-F9-WT; Norm and Alt-S1 splicing were detected in HeLa-F9-M1; while Norm, Alt-S1 and Alt-S2 splicing were detected in HeLa-F9-M2. CONCLUSION The nonsense associated altered splicing (NAS) pathway, which generated alternately spliced transcripts, might be triggered in coagulation factor IX gene with nonsense mutation.
Codon, Nonsense ; Factor IX/metabolism* ; HeLa Cells ; Humans ; Mutation ; RNA Splicing ; RNA, Messenger/metabolism*

OBJECTIVE: To explore whether casticin (CAS) suppresses stemness in cancer stem-like cells (CSLCs) obtained from human cervical cancer (CCSLCs) and the underlying mechanism. METHODS: Spheres from HeLa and CaSki cells were used as CCSLCs. DNA methyltransferase 1 (DNMT1) activity and mRNA levels, self-renewal capability (Nanog and Sox2), and cancer stem cell markers (CD133 and CD44), were detected by a colorimetric DNMT activity/inhibition assay kit, quantitative real-time reverse transcription-polymerase chain reaction, sphere and colony formation assays, and immunoblot, respectively. Knockdown and overexpression of DNMT1 by transfection with shRNA and cDNA, respectively, were performed to explore the mechanism for action of CAS (0, 10, 30, and 100 nmol/L). RESULTS: DNMT1 activity was increased in CCSLCs compared with HeLa and CaSki cells (P<0.05). In addition, HeLa-derived CCSLCs transfected with DNMT1 shRNA showed reduced sphere and colony formation abilities, and lower CD133, CD44, Nanog and Sox2 protein expressions (P<0.05). Conversely, overexpression of DNMT1 in HeLa cells exhibited the oppositive effects. Furthermore, CAS significantly reduced DNMT1 activity and transcription levels as well as stemness in HeLa-derived CCSLCs (P<0.05). Interestingly, DNMT1 knockdown enhanced the inhibitory effect of CAS on stemness. As expected, DNMT1 overexpression reversed the inhibitory effect of CAS on stemness in HeLa cells. CONCLUSION CAS effectively inhibits stemness in CCSLCs through suppression of DNMT1 activation, suggesting that CAS acts as a promising preventive and therapeutic candidate in cervical cancer.
Female ; Humans ; Cell Line, Tumor ; HeLa Cells ; Neoplastic Stem Cells/metabolism* ; RNA, Small Interfering/metabolism* ; Uterine Cervical Neoplasms/metabolism*

OBJECTIVETo investigate DNA repair in CHL cells and HeLa cells after DNA damage induced by different oxidative agents.

METHODSCHL cells and HeLa cells were exposed to various damaging agents, CHL cells: H(2)O(2) for 25 min, K(2)Cr(2)O(7) for 105 min, doxorubicin (Dox) for 75 min HeLa cells: H(2)O(2) for 25 min, K(2)Cr(2)O(7) for 105 min; then cells were continuously cultured for 0-3 h after washing. Alkaline single cell gel electrophoresis (ASCGE) assay was used to detect DNA strand breaks.

RESULT(1) DNA strand breaks were induced in CHL cells after exposure to H(2)O(2) K(2)Cr(2)O(7) or Dox, which were repaired evidently after continuous culture for 1 h(P<0.01). The damages induced by H(2)O(2) or K(2)Cr(2)O(7) were repaired completely after culture for 2-3 h. However, the demage induced by Dox was repaired incompletely. (2) DNA strand breaks were induced also in HeLa cells after exposure to H(2)O(2) or K(2)Cr(2)O(7), which were repaired evidently after continuous culture for 0.5 h(P<0.01),and completely after culture for 1 h. (3) The regression coefficient related to the rate of comet cells and repair time was statistically different (P<0.05) between CHL cells and HeLa cells.

CONCLUSIONDNA damage induced by Dox is repaired more difficult than that induced by H(2)O(2) or K(2)Cr(2)O(7). The repair initiates immediately after DNA damage in both of cells, but more rapidly in HeLa cells than in CHL cells.

DNA ; metabolism ; DNA Damage ; DNA Repair ; HeLa Cells ; Humans ; Hydrogen Peroxide ; toxicity ; Oxidation-Reduction ; Regression Analysis

OBJECTIVETo establish a transgenic cell line with stable expression of CD14.

METHODSTotal RNA extracted from peripheral blood mononuclear cells was treated with RNAase-free DNAase, the human CD14 gene was cloned and sequenced through the RT-PCR, T-A clone techniques and ABI PRISM377 machine. Eukaryotic expression vector pcDNA3.1(+)/CD14 was constructed by cleaving with double restriction endonucleases EcoR I/Xba I and ligating with T4 ligase. The human cervical cancer cell line Hela was transfected with the positive recombinant plasmid pcDNA3.1(+)/CD14 using superfect transfection reagent. Positive clones were selected by G418 at a concentration of 0.5 μg/μl and the expression of human CD14 on the transfected Hela cells was confirmed by quantitative PCR and immunofluorescent assay.

RESULTSThere was significantly difference om expression of CD14 mRNA between the blank pcDNA3.1(+) transfected cells and pcDNA3.1(+)/CD14 transfected cells (P<0.01). The fluorescence was significantly stronger on the stable cell line Hela-CD14 than that on the transiently transfected Hela cells,and no visible fluorescence was observed in blank vector transfected cells.

CONCLUSIONThe transfectant cell line Hela-CD14 with stable expression of human CD14 has been successfully established, which can be used to study human CD14 molecular and CD14-associated monocyte/macrophage cell diseases.

Female ; Gene Expression ; Genetic Vectors ; HeLa Cells ; Humans ; Lipopolysaccharide Receptors ; genetics ; metabolism ; Plasmids ; genetics ; Transfection

OBJECTIVETo investigate the time course of let-7a microRNA expression in the cell cycle of HeLa cells.

METHODSHeLa cells were synchronized in G(1), S and G(2)/M phases using double-thymidine block, and the cell cycle phases were defined by flow cytometry. Real-time quantitative RT-PCR was used to examine the expression of let-7a in HeLa cells in different cell cycle phases.

RESULTSThe synchronization rates of G(1), S and G(2)/M phases were 84.81%, 83.65% and 77.69%, respectively. Let-7a was constitutively expressed throughout the cell cycle in HeLa cells, but the expression levels in G(1) and S phases were lower than those in G(2)/M phase.

CONCLUSIONSCell cycle can significantly influence the expression level of let-7a, which may provide new clues to the understanding of the cell cycle control mechanisms.

Cell Cycle ; genetics ; Gene Expression Regulation, Neoplastic ; physiology ; HeLa Cells ; Humans ; MicroRNAs ; genetics ; metabolism

Cytoplasmic Granules ; metabolism ; Drug Evaluation, Preclinical ; methods ; Drugs, Chinese Herbal ; chemistry ; pharmacology ; HeLa Cells ; Humans

Animals ; Blastocyst ; Embryo Loss ; HeLa Cells ; Humans ; Mice ; Nuclear Proteins ; deficiency ; genetics ; metabolism

To clone human mitogen-activated protein kinase kinase 6 (MKK6) gene promoter and explore its transcription activity by ubiquitin specific peptidase 22 (USP22).
 Methods: MKK6 gene promoter was amplified by PCR and two bases mutation within USP22 binding site was subsequently introduced. The wild type and mutant MKK6 promoter were inserted into the luciferase report vector pGL3-Basic, respectively. Recombinant plasmids were co-transfected with plasmid pRL-TK into HeLa cells, and the luciferase activities were measured by dual luciferase reporter system. Furthermore, the direct interaction between USP22 and MKK6 promoter was detected by chromatin immunoprecipitation (ChIP) assay. Finally, the MKK6 transcription activity was measured after knockdown of USP22.
 Results: The recombinant luciferase report vectors containing wild or mutant type of MKK6 promoter were successfully constructed. Mutation of USP22 binding site resulted in decrease of MKK6 promoter-driven luciferase activity in HeLa cells (P<0.05). USP22 could interact directly with MKK6 promoter. Down-regulation of USP22 led to the decreased MKK6 mRNA expression (P<0.05).
 Conclusion: USP22 could regulate the transcription activity of MKK6 gene in HeLa cells.
HeLa Cells ; Humans ; Luciferases ; MAP Kinase Kinase 6 ; Promoter Regions, Genetic ; Thiolester Hydrolases ; metabolism ; Transcription, Genetic