Transcription factors regulatory domains

Fig. 4. Domain structure of mammalian DNA methyltransferases. (a) The domain structure of the known DNA methyltransferases, depicting the conserved catalytic domain (dark box) and other identified domains. Conserved aminoacid motifs in the catalytic domain are shown in lighter shade of gray. (b) Schematic representation of the reported protein-protein interactions of Dnmtl with a number of regulatory proteins interactions that modulate Dnmtl methyitransferase activity (darker rectangles) or mediate methylation-independent transcriptional repression mechanisms (lighter rectangles). When Dnmtl represses transcription through its enzymatic activity, it has been described to interact with some proteins PCNA [37] and an oncogenic transcription factor PML-RAR [25]. Note that in the case of the PML-RAR transcription factor, histone deacetylase 1 (HDACl) is also bound to the complex. When Dnmtl represses transcription via methylation-independent pathways, it binds to HDACs either directly [34] or indirectly through other proteins the corepressor DMAPl [33], the retinoblastoma protein, and a gene-specific transcription factor [31].

These are but two of the types of domains found to be involved in transcription activation. Undoubtedly, this list will grow in the near future, as will our understanding about how these transcription activation domains work. Thus far they are likely to represent regions that function by contacting other regulatory proteins, transcription factors, and the RNA polymerase itself. 

In females, the production of TRA results in the production of the femaledetermining protein DSXF. When tra is inactive (in males), dsx produces the male-determining protein DSXM (Baker et al., 1989). Each form has positive and negative regulatory functions (Burtis and Baker, 1989). Both dsx products share their N-terminal domain which is involved in DNA binding but differ in the terminal sequence, as sex-specific splicing of the last exon produces different transcription factors (Burtis and Baker, 1989 An and Wensink, 1995). 

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