HSF1 TRANSCRIPTION FACTOR CONCENTRATES IN NUCLEAR FOCI DURING HEAT-SHOCK - RELATIONSHIP WITH TRANSCRIPTION SITES

In this paper, we show that upon heat shock, HSF1 concentrates in the nucleus of diploid human fibroblasts in two large foci, The relative d istribution of HSF1 nuclear foci and active heat shock protein (hsp) g enes was investigated by combining fluorescence in situ hybridization (FISH) for the detection of hsp nuclear transcripts and immunofluoresc ence for the detection of HSF1. We show that the HSF1 foci are distinc t from the sites of hsp70 and hsp90 genes transcription. This is the s econd report of ploidy-dependent foci of transcription factors that ar e independent of their specific transcription sites. However, the corr elation between the number of HSF1 foci and the ploidy of the cells st rongly supports the existence of a specific chromosomal target for HSF 1 foci.