Serum response element associated transcription factors in mouse embryos: Serum response factor, YY1, and PEA3 factor

Many mammalian transcription factors, including human and mouse serum response factors (SRFs), are post‐translationally modified with O‐linked N‐acetylglucosamine monosaccharides on multiple serine and/or threonine residues. Nuclear extracts were prepared from 9.5 to 19 days postcoitum mouse embryos and subsequently were fractionated by wheat germ agglutinin (WGA)‐agarose affinity chromatography. SRF binds WGA‐agarose and apparently is O‐glycosylated. On the other hand, the low molecular weight serum response element (SRE)‐binding proteins, including the previously named band I and band II factors, did not bind WGA‐agarose. Furthermore, we showed that the fastest migrating complex contains the Yin‐Yang 1 (YY1) factor. YY1 binds to the c‐fos SRE and skeletal β‐actin muscle regulatory element (MRE), but not the cardiac β‐actin MRE. Nuclear extracts from NIH/3T3 fibroblasts contain similar, if not identical, SRE‐binding complexes. Besides these SRE‐binding factors, mouse PEA3‐binding factor, presumably an ETS domain‐containing protein, was found to bind SRF protein. This physical interaction, between SRF and ETS domain proteins, was shown to involve the DNA‐binding domain‐containing region of SRF and not the carboxyl‐terminal transactivation domain. © 1995 Wiley‐Liss, Inc.