Sperm chromatin decondensation by template activating factor I through direct interaction with basic proteins.
Template activating factor I (TAF-I) was originally identified as a host factor required for DNA replication and transcription of adenovirus genome complexed with viral basic proteins. Purified TAF-I was shown to bind to core histones and stimulate transcription from nucleosomal templates. Human TAF-I consists of two acidic proteins, TAF-Ialpha and TAF-Ibeta, which differ from each other only in their amino-terminal regions. Here, we report that TAF-I decondenses demembraned Xenopus sperm chromatin. Human TAF-Ibeta has a chromatin decondensation activity comparable to that of NAP-I, another histone binding protein, whereas TAF-Ialpha has only a weak activity. Analysis of molecular mechanisms underlying the chromatin decondensation by TAF-I revealed that TAF-I interacts directly with sperm basic proteins. Deletion of the TAF-I carboxyl-terminal acidic region abolishes the decondensation activity. Interestingly, the acidic region itself is not sufficient for decondensation, since an amino acid substitution mutant in the dimerization domain of TAF-I which has the intact acidic region does not support chromatin decondensation. We detected the beta form of TAF-I in Xenopus oocytes and eggs by immunoblotting, and the cloning of its cDNA led us to conclude that Xenopus TAF-Ibeta also decondenses sperm chromatin. These results suggest that TAF-I plays a role in remodeling higher-order chromatin structure as well as nucleosomal structure through direct interaction with chromatin basic proteins.
Matsumoto
K
K
Laboratory of Cellular Biochemistry, The Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-0198, Japan. matsumok@postman.riken.go.jp
Nagata
K
K
Miyaji-Yamaguchi
M
M
Kikuchi
A
A
Tsujimoto
M
M
D000595:Amino Acid Sequence; D000818:Animals; D002843:Chromatin / Q000378:metabolism* / Q000648:ultrastructure*; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D005260:Female; D056488:Histone Chaperones; D006657:Histones / Q000378:metabolism; D006801:Humans; D008297:Male; D018832:Molecular Chaperones / Q000378:metabolism; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000302:isolation & purification / Q000378:metabolism*; D009865:Oocytes / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D020539:Sequence Analysis, Protein; D017386:Sequence Homology, Amino Acid; D013094:Spermatozoa / Q000378:metabolism*; D014157:Transcription Factors; D014981:Xenopus
D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D056488:Histone Chaperones; D006657:Histones; D018832:Molecular Chaperones; D009687:Nuclear Proteins; C513473:SET protein, human; D014157:Transcription Factors