Transcriptional stimulation by the DNA binding protein Hap46/BAG-1M involves hsp70/hsc70 molecular chaperones.
The hsp70/hsc70-associating protein Hap46 of human origin, also called BAG-1M (Bcl-2-associated athanogene 1), has been characterized previously as a DNA binding protein, which is able to stimulate transcription. By use of in vitro assays we now show that Hap46-mediated transcriptional activation can occur from linearized as well as from supercoiled circular DNA and does not require the presence of a transcription promoter. Accordingly, we observed no preferential binding of Hap46 to overlapping DNA fragments covering the sequence of the cytomegalovirus (CMV) early promoter, thus suggesting non-specific binding. The C-terminal deletion variant Hap46DeltaC47, which is unable to associate with hsp70/hsc70 molecular chaperones, produced greatly diminished effects on transcription, indicating a significant involvement of hsp70/hsc70 chaperones but not an absolute requirement. In contrast, deletion of the acidic hexarepeat region, as in variant Hap46Delta12-62, did not disturb transcriptional stimulation. While full-length Hap46 readily formed complexes with a series of structurally unrelated transcription factors, variant Hap46DeltaC47 proved incapable of doing so. Together these data suggest that transcriptional stimulation is a major biological activity of Hap46 and point to involvement of hsp70/hsc70 molecular chaperones in transcription in concert with Hap46, thus providing a link between hsp70/hsc70 molecular chaperones and components of the transcription machinery.
Niyaz
Yilmaz
Y
Molekulare Evolution und Genomik, Im Neuenheimer Feld 230, and Biochemie-Zentrum Heidelberg, D-69120 Heidelberg, Germany.
Frenz
Irina
I
Petersen
Gabriele
G
Gehring
Ulrich
U
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D019556:COS Cells; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D003587:Cytomegalovirus / Q000235:genetics; D004247:DNA / Q000235:genetics / Q000378:metabolism*; D004270:DNA, Circular / Q000235:genetics / Q000378:metabolism; D004279:DNA, Viral / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins; D024202:Electrophoretic Mobility Shift Assay; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D014157:Transcription Factors; D014158:Transcription, Genetic / Q000235:genetics; D015533:Transcriptional Activation
C091732:BCL2-associated athanogene 1 protein; D002352:Carrier Proteins; D004270:DNA, Circular; D004279:DNA, Viral; D004268:DNA-Binding Proteins; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; C494371:HSPA8 protein, human; D018832:Molecular Chaperones; D011960:Receptors, Estrogen; D014157:Transcription Factors; D004247:DNA