NUCLEOSOME POSITIONING BY THE WINGED HELIX TRANSCRIPTION FACTOR HNF3

Nucleosome positioning at genetic regulatory sequences is not well und erstood. The transcriptional enhancer of the mouse serum albumin gene is active in liver, where regulatory factors occupy their target sites on three nucleosome-like particles designated N1, N2, and N3. The win ged helix transcription factor HNF3 binds to two sites near the center of the N1 particle. We created dinucleosome templates using the album in enhancer sequence and found that site-specific binding of HNF3 prot ein resulted in nucleosome positioning in vitro similar to that seen i n liver nuclei. Thus, binding of a transcription factor can position a n underlying nucleosome core.