Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Microtubules play an essential role in cell division. Little is known about possible variations of total tubulin and tubulin isotype expression during the cell cycle. We analyzed the total tubulin content, tubulin polymerization status and tubulin isotype content in resting and dividing human K562 leukemic cells and human MES-SA sarcoma cells. Although the total cellular tubulin content increases as the cells progress toward mitosis, the total tubulin/total protein ratio is stable during the cell cycle. Reverse transcriptase-polymerase chain reaction was applied to analyze the levels of expression of alpha, beta, and gamma-tubulin isotypes. Whereas alpha-tubulin isotype and gamma-tubulin transcripts were found to be expressed at constant levels throughout the cell cycle, some of the beta-tubulin isotype transcripts were found to be more highly expressed in dividing then in resting cells. Both of the class IV beta-tubulin isotype transcripts (human 5 beta and beta 2, Class IVa and IVb, respectively) were expressed in dividing K562 and MES-SA cells at twice the levels found in resting cells. Increased expression of the class IV isotype proteins in dividing cells was confirmed by immunoblotting, both in K562 and in MES-SA cells. A larger fraction of total cell tubulin was found to be polymerized in dividing cells (36-40%) than in resting cells (27-30%). The degree of polymerization of class IV tubulin in dividing and resting cells was similar to that of total tubulin. These results show that total tubulin is expressed as constant levels throughout the cell cycle but that the degree of polymerization is increased as cells are committed to division. The relative overexpression of the two class IV beta-tubulin isotypes in dividing cells suggests functional specificity for these isotypes and a regulatory role of these isotypes on the microtubule network during mitosis.
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PMID:Differential expression of tubulin isotypes during the cell cycle. 887 65

A 1.3Mb chromosome 11-specific yeast artificial chromosome (YAC) that spans a t(1;11) translocation breakpoint associated with major psychosis has been used to enrich cDNAs that are encoded within it and expressed in the human foetal brain. Database analysis of the selected fragments led to the identification of 54 clones matching alpha-tubulin, 4 fragments matching two anonymous human expressed sequence tags (ESTs) and 8 fragments giving no database matches. The clones matching alpha-tubulin led to the identification of a novel alpha-tubulin locus located approximately 250 kb proximal to the translocation breakpoint. Extensive sequence and expression analysis of this locus suggests that this is a processed pseudogene, although a long open reading frame is maintained and the possibility that an abnormally acting protein may be expressed in a highly tissue or developmental specific manner cannot be discounted. The novel cDNA fragments map up to 700 kb proximal to the translocation breakpoint and are associated with potential CpG islands. Reverse transcriptase polymerase chain reaction (RT-PCR) expression analysis and high resolution genomic mapping suggest that they may comprise up to three novel genes. No major disruption of the identified fragments could be detected in the genomic DNA of translocation carriers. The psychosis associated with this translocation may therefore be due to position effects on the transcription of these genes or an involvement of translocated chromosome 1 sequences.
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PMID:Novel transcribed sequences neighbouring a translocation breakpoint associated with schizophrenia. 903 12

It has been long known that neoplastic transformation is accompanied by a lowered requirement for extracellular Ca2+ for growth. The studies presented here demonstrate that human fibroblastic cell lines produce the two commonly found 'housekeeping' isoforms of the plasma membrane Ca(2+)-ATPase (PMCA), PMCA1b and 4b, and at the expression of both is demonstrably lower in cell lines neoplastically transformed by SV40 than in the corresponding parental cell lines. Western blot analyses of lysates from control (GM00037) and SV40-transformed (GM00637) skin fibroblasts revealed a 138 kDa PMCA whose level was significantly lower in the SV40-transformed cells relative to either total cellular protein or alpha-tubulin. Similar analyses of plasma membrane preparations from control WI-38) and SV40-transformed (WI-38VA13) lung fibroblasts revealed 3-4-fold lower levels of PMCA in the SV40-transformed cells. Competitive ELISAs performed on detergent solubilized plasma membrane preparations indicated at least 3-4-fold lower levels of PMCA in the SV40-transformed cell lines compared to controls. Reverse transcriptase coupled-PCR analyses showed that PMCA1b and PMCA4b were the only isoforms expressed in all four cell lines. The PMCA4b mRNA level detected by Northern analysis also was substantially lower in SV40 transformed skin fibroblasts than in non-transformed fibroblasts. Quantitative RT-PCR analyses showed levels of PMCA1b and 4b mRNAs to be 5 and 10-fold lower, respectively, in GM00637 than in GM00037 when the levels of PCR products were normalized to glyceraldehyde-3-phosphate dehydrogenase (G3PDH) mRNA. These results demonstrate that the expression of these distinct PMCA genes is substantially lower in SV40 transformed human skin and lung fibroblasts and may be coordinately regulated in these cells.
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PMID:Analysis of plasma membrane Ca(2+)-ATPase expression in control and SV40-transformed human fibroblasts. 905 77

The experiments described herein were designed to determine whether tumor necrosis factor alpha (TNF-alpha) displays a diurnal variation in various areas of the normal rat brain. TNF-alpha mRNA transcripts were detected by reverse-transcriptase polymerase chain reaction. To monitor diurnal changes in TNF-alpha and alpha-tubulin expression, rats were sacrificed every 4 h for 24 h starting 1 h after light onset; relative mRNA levels were determined for the cerebellum, cortex, hippocampus, hypothalamus and brainstem. TNF-alpha mRNA was higher during the light than in the dark phase in the hypothalamus and hippocampus. alpha-Tubulin mRNA exhibited a similar diurnal variation in the hypothalamus, hippocampus and cortex. In contrast, beta-actin mRNA was lower during the light phase than the dark phase in the hippocampus and cortex. The observed diurnal variations in TNF-alpha mRNA are consistent with the hypothesis that TNF has a physiological role in the brain.
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PMID:Diurnal variations of tumor necrosis factor alpha mRNA and alpha-tubulin mRNA in rat brain. 948 99

Reverse-transcriptase polymerase chain reaction cloning of the 3'-ends of the alpha-tubulin cDNAs of Tritrichomonas mobilensis in combination with Southern-blot analysis identified seven to eight distinct alpha-tubulin genes. All seven lack a carboxy-terminal tyrosine and the corresponding sequence compatible with posttranslational tyrosination. This indicates that whereas tyrosination of alpha-tubulin has been found in most species, including humans and trypanosomes, it is absent in trichomonads.
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PMID:Alpha-tubulins of Tritrichomonas mobilensis are encoded by multiple genes and are not posttranslationally tyrosinated. 995 70

The recent advances on the cytoplasmic regulators of the induction of germinal vesicle break down, maturation and degeneration of oocytes, and glycosaminoglycan composition during cumulus expansion of cumulus-oocyte complexes are discussed. A) Inactive mitogen-activated protein kinases (MAPKs) are present in the oocytes at germinal vesicle (GV) stage, and are activated with germinal vesicle breakdown (GVBD), and remain highly active throughout maturation in porcine oocytes. Inactive MAPKs are localized in the cytoplasm of GV-arrested oocytes and active MAPKs were detected in the GV just before GVBD. B) Cumulus expansion of porcine cumulus-oocyte complexes (COCs) was reduced by oocy tectomy. The profile of total glycosaminoglycan synthesis was attributed to hyaluronic acid rather than chondroitin sulfate in intact COCs and oocytectomy reduced hyaluronic acid synthesis. C) The abnormalities of chromosomes and alpha-tubulin morphology were observed in the oocytes of c-mos deficient mice. MAPK activity of c-mos deficient oocytes did not significantly fluctuate throughout maturation and was clearly lower than that of wild-type oocytes. One of the most drastic abnormalities in c-mos knockout mouse oocytes was their entrance into the interphase instead of second meiosis after first polar body emission. D) Reverse transcriptase/polymerase chain reaction-Southern blot hybridization demonstrated positive expression of Fas in intraovarian mouse oocytes. In contrast, expression of Fas ligand was detected in granulosa cells. These findings were histologically confirmed by in situ hybridization with Fas- and FasL-specific probes. Co-culture of intact and zona-free eggs and granulosa cells demonstrated positive TUNEL staining only zona-free eggs.
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PMID:Morphological dynamics of cumulus-oocyte complex during oocyte maturation. 1131 42