Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.21.1 (DNase)
 7,655 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Poly(ADP-ribosyl)ation of nuclear proteins was several-fold higher in the pachytene spermatocytes than in the premeiotic germ cells of the rat. Among the histones of the pachytene nucleus, histone subtypes H2A, H1 and H3 were poly(ADP-ribosyl)ated. Based on the immunoaffinity fractionation procedure of Malik, Miwa, Sugimara & Smulson [(1983) Proc. Natl. Acad. Sci. U.S.A. 80, 2554-2558] we have fractionated DNAase-II-solubilized chromatin into poly(ADP-ribosyl)ated chromatin (PAC) and non-poly(ADP-ribosyl)ated chromatin (non-PAC) domains on an anti-[poly(ADP-ribose)] IgG affinity matrix. Approx. 2.5% of the pachytene chromatin represented the PAC domains. A significant amount of [alpha-32P]dATP-labelled pachytene chromatin (labelled in vitro) was bound to the affinity matrix. The DNA of pachytene PAC domains had internal strand breaks, significant length of gaps and ligatable ends, namely 5'-phosphoryl and 3'-hydroxyl termini. On the other hand, the PAC domains from 18 h regenerating liver had very few gaps, if any. The presence of gaps in the pachytene PAC DNA was also evident from thermal denaturation studies. Although many of the polypeptides were common to the PAC domains of both pachytene and regenerating liver, the DNA sequences associated with these domains were quite different. A 20 kDa protein and the testis-specific histone H1t were selectively enriched in the pachytene PAC domains. The pachytene PAC domains also contained approx. 10% of the messenger coding sequences present in the DNAase-II-solubilized chromatin. The pachytene PAC domains, therefore, may represent highly enriched DNA-repair domains of the pachytene nucleus.
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PMID:Characterization of poly(ADP-ribosyl)ated domains of rat pachytene chromatin. 280 42

The testis-specific histone H1t is synthesized exclusively in late pachytene primary spermatocytes during spermatogenesis. The mechanisms involved in transcriptional repression of the H1t gene during development before the spermatocyte stage and in later stages of germinal cell maturation and in nonexpressing somatic tissues are unknown. To assess the contribution of the upstream DNA sequence to H1t transcriptional silencing in nonexpressing cells, a set of histone H1t-promoted reporter vectors was constructed. Transient transfection of mouse C127I cells with these reporter vectors allowed us to identify a transcriptional silencer located between 948 base pairs (bp) and 780 bp upstream from the H1t transcriptional initiation site. Histone H1t-promoted luciferase activity increased 4-fold when the region between 948 bp and 875 bp upstream from the transcriptional initiation site was eliminated. Addition of a 73-bp rat H1t promoter fragment (-948 to -875, containing the 5' portion of the silencer region) to a site immediately upstream from the histone H1d proximal promoter led to significantly reduced luciferase expression upon transient transfection (56% in C127I cells and 44% in HeLa cells). Nuclear proteins were found to bind to DNA within the H1t silencer region when assayed by in vitro deoxyribonuclease (DNase) I footprinting. Thus, our data suggest that an active transcriptional silencer mechanism involving a specific and autonomous H1t promoter element (nucleotides -948/-875) may be operative to minimize expression of the H1t gene in nontesticular cells.
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PMID:Localization of upstream elements involved in transcriptional regulation of the rat testis-specific histone H1t gene in somatic cells. 1049 37