(1) Laboratory of Biotechnology,
University of Bergen
(2) Gene Expression Programme, EMBL, Meyerhofstrasse 1, D-69117 Heidelberg. Germany
Trends Biochem. Sci (TiBS) 21:87-88 (1996) - March issue.
TiBS is published by Elsevier
We found the SANT domains as a repeated motif in N-CoR, the nuclear receptor co-repressor (Hoerlein et al., 1995). Subsequent searches revealed that SANT domains occur as doublets or singlets in many different proteins. Most notably, we find single copies of the SANT domains in the yeast nuclear proteins SWI3, ADA2 and TFIIIB''. The SWI3 protein is a componenet of the SWI/SNF complex, a global transcriptional activator (Peterson and Tamkun, 1995). The ADA2 protein is part of the ADA (or adaptor) complex (Horiuchi et al., 1995) and TFIIIB'' is a subunit of the basal trascription factor TFIIIB required for polIII transcription in yeast (Kassavetis et al., 1995).
Sequence searches with SANT domains consistently picked up the DNA binding domains of MYB-like proteins and, indeed, the SANT domains can be aligned to MYB repeats (see alignment ). A secondary structure prediction supports this observation, indicating that the SANT domains are fold into three alpha helices. The similarity of SANT domains to MYB domains strongly suggest that SANT domains are DNA binding domains.
Quinn et al. (1996) recently
showed that the SWI/SNF complex has a DNA binding activity. And here is
some more information on the components of the SWI/SNF
A further development in the elucidation of the function of SANT-proteins comes with the identification by Brownell et al. (1996) of GCN5, another component of the ADA-complex, as a histone acetyl transferase A.