Mixed linked leukemia 4 (MLL4) is a specific methyltransferase of histone 3 position lysine 4 (H3K4). It is also one of the important members of COMPASS/Set1-like protein complex. Both MLL4 protein itself and its mediated H3K4 methylation modification can cause changes in chromatin structure and function, thus regulating gene transcription and expression. With the studies of MLL4 protein in recent years, the roles of MLL4 gene, MLL4 protein and protein complex in the development of tissues and organs, tumor diseases and other physiological and pathophysiological processes have been gradually revealed. In this paper, the research progress of MLL4 gene, MLL4 protein characteristics, biological function and its effect on disease were reviewed, in order to further understand the effect of histone methyltransferase on gene expression regulation, as well as its non-enzyme dependent function. This paper may provide new ideas for the prevention, diagnosis and treatment of related diseases.
DNA-Binding Proteins ; physiology ; Histone-Lysine N-Methyltransferase ; physiology ; Histones ; chemistry ; Humans ; Methylation

As an important telomere binding protein, TPP1 protects the ends of telomeres and maintains the stability and integrity of its structure and function by interacting with other five essential core proteins (POT1, TRF1, TRF2, TIN2, and RAP1) to form a complex called Shelterin. Recently, researchers have discovered that TPP1 participates in protection of telomeres and regulation of telomerase activity. The relationship between TPP1 and tumorigenesis, tumor progression and treatment has also been investigated. This paper reviews the latest findings of TPP1 regarding to its structure, function and interaction with other proteins involved in tumorigenesis.
Chromosomal Instability ; DNA Damage ; Humans ; Neoplasms ; genetics ; Telomere ; Telomere-Binding Proteins ; chemistry ; physiology

PURPOSETo review the recent developments in the structure and function of Smad proteins.

DATA SOURCESBoth Chinese- and English-language literatures were searched using MEDLINE/CD-ROM (1997 - 2000) and the Index of Chinese-Language Literature (1997 - 2000).

STUDY SELECTIONData from published articles about TGF-beta signal transduction in recent domestic and foreign literature were selected.

DATA EXTRACTIONData were mainly extracted from 22 articles which are listed in the reference section of this review.

RESULTSSmad proteins mediate signal transduction induced by the TGF-beta superfamily. Based on their structural and functional properties, Smad proteins are divided into three groups. The first group, receptor-regulated Smads (R-Smads), are phosphorylated by activated type I receptors and form heteromeric complexes with the second group of Smads, common mediator Smads (Co-Smads). These Smad complexes translocate into the nucleus to influence gene transcription. Inhibitory Smads (I-Smads) are the third group and these antagonize the activity of R-Smads. In the nucleus, Smads can directly contact Smad-binding elements (SBE) in target gene promoters. Through interaction with different transcription factors, transcriptional co-activators or co-repressors, Smads elicit different effects in various cell types. The aberrance of Smad proteins has been noted in several human disorders such as fibrosis, hypertrophic scarring and cancer.

CONCLUSIONThe structure of Smads determines their function as transcriptional factors which translocate signals from the cell surface to the nucleus where Smads regulate TGF-beta superfamily-dependent gene expression.

DNA-Binding Proteins ; chemistry ; physiology ; Humans ; Signal Transduction ; Smad Proteins ; Trans-Activators ; chemistry ; physiology ; Transcription Factors ; physiology ; Transforming Growth Factor beta ; physiology

Common warts are close associated with HPVs infection. In this study, we amplified and sequenced the LCR fragment and E2 gene of HPV-2 that infected the patient of extensive common wart with cutaneous horns, and we constructed the recombinant CAT-reporter plasmids pBLCAT-LCR containing HPV-2 prototype or variant LCR and mammalian expression plasmids pcDNA3. 1-E2 containing prototype or variant E2 ORF individually. The promoter activities of HPV-2 variant and the transcriptional repression activities of the mutated E2 protein were evaluated by transient transfection into HeLa cells. The results showed that there were several mutations in LCR and E2 gene of HPV-2 variant. Compared with the prototype, the viral early promoter activity of variant was significantly increased uder the control of LCR. Compared with the wild type E2 protein, the transcriptional repression activities of the mutated E2 protein was abolished partially. We speculate herein that increased promoter activities and decreased repression effect of the mutated E2 protein are linked, at least partially, with the clinical phenotypes of the uncommon huge common wart.
DNA-Binding Proteins ; genetics ; physiology ; Humans ; Mutation ; Oncogene Proteins, Viral ; genetics ; physiology ; Papillomaviridae ; genetics ; Promoter Regions, Genetic ; Repressor Proteins ; physiology ; Warts ; virology

The low dose hyper-radiosensitivity (HRS) in human lung cancer cell line A549 was investigated, the changes of ATM kinase, cell cycle and apoptosis of cells at different doses of radiation were observed, and the possible mechanisms were discussed. A549 cells in logarithmic growth phase were irradiated with (60)Co gamma-rays at doses of 0-2 Gy. Together with flow cytometry for precise cell sorting, cell survival fraction was measured by means of conventional colony-formation assay. The expression of ATM1981Ser-P protein was examined by Western blot 1 h after radiation. Apoptosis was detected by Hoechst 33258 fluorescent staining, and Annexin V-FITC/PI staining flow cytometry 24 h after radiation. Cell cycle distribution was observed by flow cytometry 6, 12 and 24 h after radiation. The results showed that the expression of ATM1981Ser-P protein was observed at 0.2 Gy, followed by an increase at >0.2 Gy, and reached the peak at 0.5 Gy, with little further increase as the dose exceeded 0.5 Gy. Twenty-four h after radiation, partial cells presented the characteristic morphological changes of apoptosis, and the cell apoptosis curve was coincident with the survival curve. As compared with control group, the cell cycle almost had no changes after exposure to 0.1 and 0.2 Gy radiation (P>0.05). After exposure to 0.3, 0.4 and 0.5 Gy radiation, G(2)/M phase arrest occurred 6 and 12 h after radiation (P<0.05), and the ratio of G(2)/M phase cells was decreased 24 h after radiation (P<0.05). It was concluded that A549 cells displayed the phenomenon of HRS/IRR. The mode of cell death was mainly apoptosis. The activity of ATM and cell cycle change may take an important role in HRS/IRR.
Cell Cycle Proteins/genetics ; Cell Cycle Proteins/metabolism ; Cell Cycle Proteins/physiology ; Cell Line, Tumor ; DNA-Binding Proteins/antagonists & inhibitors ; DNA-Binding Proteins/metabolism ; DNA-Binding Proteins/*physiology ; Dose-Response Relationship, Radiation ; Lung Neoplasms/*pathology ; Protein-Serine-Threonine Kinases/*metabolism ; Radiation Dosage ; Radiation Tolerance/*physiology ; Tumor Suppressor Proteins/metabolism

OBJECTIVETo synthesize highly pure HBV post-transcriptional regulatory element (HPRE) via transcription in vitro by T7 RNA polymerase.

METHODSHPRE gene was amplified by PCR from a template containing HBV complete genomic DNA and cloned into plasmid pGEM-11zf. The cloned DNA sequence was transcribed by T7 RNA polymerase.

RESULTSThe construction of HPRE gene recombinant plasmid and production of HPRE via transcription in vitro was successful.

CONCLUSIONIn vitro transcription by T7 RNA polymerase can be used to synthesize highly pure HPRE.

DNA-Directed DNA Polymerase ; DNA-Directed RNA Polymerases ; Hepatitis B virus ; genetics ; RNA Processing, Post-Transcriptional ; RNA Splicing ; RNA-Binding Proteins ; physiology ; Transcription, Genetic ; Viral Proteins

OBJECTIVETo establish a new non-radioactive method for electrophoretic mobility shift assay (EMSA) to investigate the binding between glucocorticoid induced leucine zipper (GILZ) and peroxisome proliferator-activated receptor-gamma 2 (PPARgamma2) promoter oligonucleotides.

METHODSGILZ protein prepared by prokaryotic expression was linked to PPARgamma2 promoter oligonucleotides end-labeled with IRDye 800 infrared dye. The DNA-protein complex was separated with non-denatured polyacrylamide gel and scanned with the Odyssey. Infrared Imaging System.

RESULTSOne lane of DNA-protein complex was clearly presented, and the signal intensity increased along with the increment of the protein load.

CONCLUSIONThis infrared imaging system can be used for EMSA for detecting the DNA-protein complex with high sensitivity efficiency and allows easy operation.

Binding Sites ; DNA ; chemistry ; DNA-Binding Proteins ; chemistry ; metabolism ; Electrophoretic Mobility Shift Assay ; instrumentation ; methods ; Fluorescent Dyes ; chemistry ; Gene Expression Regulation ; Humans ; Infrared Rays ; Protein Binding ; Protein Interaction Domains and Motifs ; physiology ; Proteins ; chemistry

MRE11 plays an important role in the signal transduction of DNA damage response, therefore this study was purposed to explore the relationship between hMRE11 focus formation and DNA double-strand breaks (DSBs) caused by etoposide (VP-16) in human promonocytic cells U937. After U937 cells were treated with VP-16, the drug-induced DSBs were assessed by pulsed-field gel electrophoresis (PFGE), the gene transcription levels of hMRE11 were evaluated by RT-PCR, the nuclear focus formation of hMRE11 protein was examined using immunofluorescence technique, the cell cycle in parallel was analyzed by flow cytometry. The results showed that the percentage of U937 cells with DSBs induced by VP-16 raised from 13.0 +/- 2.3% in VP-16 2 microg/ml to 32.0 +/- 4.3% in VP-16 20 microg/ml (P < 0.01) along with increase of VP-16 dose. No difference of the hMRE11 mRNA level in U937 cells following the treatment with 100 microg/ml VP-16 at different times was discovered (P > 0.05). The hMRE11 protein was abundantly and uniformly distributed in the nuclei of untreated U937 cells outside of nucleoli, however, it formed discrete nuclear foci following VP-16 treatment. The mean value of nuclear foci increased by 5 to 20 times following the drug dosing (P < 0.01). An average of 5 nuclear foci per positive nucleus were observed at a dose of 2 microg/ml, and it was increased to an average of over 14 nuclear foci per positive nucleus after treating with VP-16 20 microg/ml. The percentage of nuclei containing hMRE11 nuclear foci also increased from less than 10% after treatment wiht VP-16 2 microg/ml to over 50% after VP-16 20 microg/ml (P < 0.01) following treatment with VP-16. After U937 cells were treated with 100 microg/ml VP-16 for 2 hours and fixed at 4, 8, 12 and 24 hours, the percentage of nuclei with hMRE11 nuclear foci increased to 61.54 +/- 3.6% (the control U937 cells: 0.47 +/- 1.17%, P < 0.01) at 8 hours, with a subsequent decrease in the percentage of nuclear foci-positive cells by 24 hours. The ratio of S-phase U937 cells at 8 hours after being treated with 100 microg/ml VP-16 for 2 hours was 47.55 +/- 2.35%, and that without 100 microg/ml VP-16 was 21.95 +/- 2.91% (P < 0.05). It is concluded that the nuclear focus formation of hMRE11 protein may be a response to DNA damage induced by topoisomerase II inhibitor VP-16 in human promonocytic cell line U937.
Antineoplastic Agents, Phytogenic ; pharmacology ; DNA Damage ; DNA Repair ; genetics ; physiology ; DNA-Binding Proteins ; biosynthesis ; genetics ; metabolism ; physiology ; Dose-Response Relationship, Drug ; Etoposide ; pharmacology ; Humans ; MRE11 Homologue Protein ; Protein Binding ; RNA, Messenger ; biosynthesis ; genetics ; Signal Transduction ; Topoisomerase II Inhibitors ; U937 Cells

To investigate the change of telomerase activity and human telomerase reverse transcriptase (hTERT) gene expression in HL-60 cells transfected with wild type p53 gene, wild type p53 gene was introduced into HL-60 cells by Lipofectin transfection. Apoptosis was analyzed by TUNEL assay. Telomerase activity and the level of hTERT mRNA were detected by telomeric repeat amplification protocol (TRAP)-ELISA and RT-PCR, respectively. The results showed that the apoptotic rate of HL-60-pN53cG cells was 8.3% and 21.0% respectively after cultured at 32.5 degrees C for 24 h and 72 h. The level of hTERT mRNA was decreased to 68.4% and 55.8% and telomerase activity to 27.3% and 8.9% of control value in HL-60-pN53cG cells at the same points. In conclusions, hTERT mRNA and telomerase activity were down-regulated in HL-60 cells transfected with p53 gene. This may be one of mechanisms of apoptosis induced by wild type p53 gene.
Apoptosis ; DNA-Binding Proteins ; Gene Expression ; Genes, p53 ; physiology ; HL-60 Cells ; Humans ; RNA, Messenger ; analysis ; Telomerase ; genetics ; metabolism

The axon initial segment (AIS) is a specialized structure that controls neuronal excitability via action potential (AP) generation. Currently, AIS plasticity with regard to changes in length and location in response to neural activity has been extensively investigated, but how AIS diameter is regulated remains elusive. Here we report that COUP-TFI (chicken ovalbumin upstream promotor-transcription factor 1) is an essential regulator of AIS diameter in both developing and adult mouse neocortex. Either embryonic or adult ablation of COUP-TFI results in reduced AIS diameter and impaired AP generation. Although COUP-TFI ablations in sparse single neurons and in populations of neurons have similar impacts on AIS diameter and AP generation, they strengthen and weaken, respectively, the receiving spontaneous network in mutant neurons. In contrast, overexpression of COUP-TFI in sparse single neurons increases the AIS diameter and facilitates AP generation, but decreases the receiving spontaneous network. Our findings demonstrate that COUP-TFI is indispensable for both the expansion and maintenance of AIS diameter and that AIS diameter fine-tunes action potential generation and synaptic inputs in mammalian cortical neurons.
Action Potentials ; Animals ; Axon Initial Segment ; COUP Transcription Factor I ; DNA-Binding Proteins/physiology* ; Mammals ; Mice ; Transcription Factors