HMGA1 mediates the activation of the CRYAB promoter by BRG1.

alphaB-Crystallin (CRYAB) is a small heat-shock protein that is implicated in many cellular processes, such as transcription and differentiation, as well as pathologic process. It is expressed at high levels in vertebrate eye lens and at low levels in a variety of other cell types. We previously identified CRYAB as a target gene of the chromatin-remodeling SWI/SNF-like Brg or hBrm-associated factors (BAF) complexes. In this report, we identify a 30 bp DNA element required for mediating the activation of CRYAB by brahma-related gene 1 (BRG1). This BRG1-response element is located at the edge of a positioned nucleosome immediately upstream of the transcription initiation site. An AT-rich sequence within this region is bound by the high-mobility group AT-hook 1 (HMGA1) proteins in vitro and in vivo. We demonstrate that the HMGA1 target sequences and HMGA1 proteins are required for the maximal activation of the CRYAB promoter by BRG1. Our data indicate that HMGA1 nonhistone chromatin proteins, the SWI/SNF chromatin remodeling complexes, and sequence-specific transcription factors act together to regulate the expression of the CRYAB gene.