Histone fold protein Dls1p is required for Isw2-dependent chromatin remodeling in vivo

We report the identification of two new subunits of the Isw2 chromatin-remodeling complex in Saccharomyces cerevisiae. Both proteins, Dpb4p and Yj1065cp (named Dls1p), contain histone fold motifs and are homologous to the two smallest subunits of ISWI-containing CHRAC complexes in higher eukaryotes. Dpb4p is also a subunit of the DNA polymerase epsilon (pole) complex, and DlsIp is homologous to another pole subunit, Dpb3p. Therefore, these small histone fold proteins may fulfill functions that are required for both polp- and Isw2 complexes. We characterized the role of Dls1p in known roles of the Isw2 complex in vivo. Transcriptional analyses reveal that the Isw2 complex requires Dls1p to various degrees at a wide variety of loci in vivo. Consistent with this, Dls1p is required for Isw2-dependent chromatin remodeling in vivo, although the requirement for this protein varies among Isw2 targets. Dls1p is likely required for functions of the Isw2 complex at steps subsequent to its interaction with chromatin, since a dls1 mutation does not affect cross-linking of Isw2 with chromatin.