Isolation and characterization of the human and mouse homologues (SUPT4H and Supt4h) of the yeast SPT4 gene

To study gene regulation mediated by chromatin in mammals, we isolated the human (SUPT4H) and murine (Supt4h) counterparts of the yeast gene encoding SPT4; the product of this gene presumably interacts with the products of the mammalian homologues (which we have also cloned) of yeast SPT5 and SPT6, thereby modulating chromatin formation and activity. We isolated two different sized human SUPT4H cDNA clones (1464 and 728 nt) and one murine Supt4h (688 nt) cDNA clone; all three encode the same 117-amino-acid protein with conservation of the zinc finger motif found in SPT4. Conservation of this zinc finger motif from yeast to mouse and human implies functional importance. Although the overall sequence homology at the DNA level between the human 728-nt transcript and the murine 688-nt transcript is only 78.4%, the DNA sequence homology is 97.7% within the coding region. At the protein level, the amino acid sequences of the translated murine Supt4h and the human SUPT4H gene products are identical. The likely functional copy of SUPT4H, which has at least two introns, maps to human chromosome 17, with candidate intronless pseudogenes on chromosomes 2, 12, and 20. Buttressing the hypothesis that this is a gene required constitutively, both the human SUPT4H transcripts and the murine Supt4h transcript are expressed widely, although not at equal levels (e.g., such as most histones), in all fetal and adult tissues that we examined.

Identification and analysis of the human and murine putative chromatin structure regulator SUPT6H and Supt6h

We have isolated and sequenced SUPT6H and Supt6h, the human and murine homologues of the Saccharomyces cerevisiae and Caenorhabditis elegans genes SPT6 (P using 1603 aa = 6.7 e-95) and emb-5 (P using 1603 aa = 7.0 e-288), respectively. The human and murine SPT6 homologues are virtually identical, as they share >98% identity and >99% similarity at the protein level. The derived amino acid sequences of these two genes predict a 1603-aa protein (human) and a 1726-bp protein (mouse), respectively. There were several known features, including a highly acidic 5'-region, a degenerate SH2 domain, and a leucine zipper. These features are consistent with a nuclear protein that regulates transcription, whose extreme conservation underscores the likely importance of this gene in mammalian development. Expression of human and murine SPT6 homologues was analyzed by Northern blotting, which revealed a 7. 0-kb transcript that was expressed constitutively. The SPT6 homologue was mapped to chromosome 17q11.2 in human by somatic cell hybrid analysis and in situ hybridization. These data indicate that SUPT6H and Supt6h are functionally analogous to SPT6 and emb-5 and may therefore regulate transcription through establishment or maintenance of chromatin structure.