Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.30.1 (S1 nuclease)
 3,660 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Telomeric heterochromatin can be demonstrated in Allium cepa chromosomes when root tip squashes are subjected to a C-banding procedure (treatment with saturated barium hydroxide for 10 min, followed by 1 h in phosphate buffer at 60 degrees C). Acridine orange (A0) staining indicated that the chromosomal DNA was denatured by the alkaline treatment and that it renatured within the first 3-7 min in the hot buffer. The DNA of the telomeres reannealed somewhat faster than the rest of the chromosomal DNA, but the AO staining suggested that all chromosomal DNA was double stranded after 7 min in buffer. Digestion of the chromosomes with a single strand specific nuclease, DNase S1, followed by Feulgen staining, demonstrated that the AO staining gives a somewhat misleading picture of the extent of DNA denaturation and renaturation. The S1 nuclease results showed that the chromosomal DNA was completely denatured by the alkaline treatment, but that a fraction of the DNA reannealed during the deionized water wash that preceded the incubation in hot buffer. Neither controls nor chromosomes subjected to the complete C-banding procedure were affected by S1 nuclease digestion, demonstrating that virtually all of the chromosomal DNA was double stranded both before and after the C-banding process. These results, along with the fact that the appearance of the bands was unaffected when the buffer incubation was performed at high (80 degrees C) or low (40 degrees C) temperature, indicated that differential DNA denaturation and renaturation is unlikely to be responsible for C-banding in this species.
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PMID:Differential rates of DNA denaturation and renaturation in situ in relation to the C-banding of Allium cepa chromosomes. 75 82

HES-1 is a mammalian helix-loop-helix factor structurally related to the Drosophila hairy and Enhancer of split proteins. It binds more preferentially to the N box (CACNAG) than to the E box (CANNTG) and acts as a negative regulator. In this study, we have isolated and characterized the mouse HES-1 gene. This gene consists of four exons, and the positions of introns are well conserved when compared with those of the Drosophila hairy gene, except for the third intron. Southern blot and interspecies backcross analyses suggest that the mouse HES-1 gene is a single-copy gene and is located around position 26 on chromosome 16. The transcription initiation site, determined by the S1 nuclease and primer extension experiments, is located 31 nucleotides downstream of a TATA box. In the 5'-regulatory region, there are four N box sequences, and the DNase I foot-printing and gel mobility shift analyses show that HES-1 binds to these sequences. Transient transfection assays using C3H10T1/2 cells suggest that there are several positive regulatory regions in the HES-1 gene. However, cotransfection of the HES-1 expression vector leads to approximately 40-fold repression in promoter activity. Furthermore, when the N box sequences are disrupted, this negative regulation is severely impaired. These results raise the possibility that HES-1 gene expression may be negatively autoregulated through the N box sequences.
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PMID:Structure, chromosomal locus, and promoter analysis of the gene encoding the mouse helix-loop-helix factor HES-1. Negative autoregulation through the multiple N box elements. 790 73