An inverted sea urchin histone gene sequence with breakpoints between TATA boxes and mRNA cap sites.

A sea urchin histone gene fragment containing inverted regions of the normal repeat has been cloned in pBR322. Restriction enzyme mapping and homoduplex analysis of this fragment indicate that the H1-H4 spacer of one repeat is situated alongside the inverted H2A-H1 spacer of another repeat. The site of the breakpoint has been sequenced and compared with homologous stretches of the normal repeat. The breakpoints in the original duplexes were found to be within 4-6 bp of the H4 mRNA cap site and 8-10 bp of the H1 mRNA cap site in the standard repeat. The breakpoints in both original duplexes contain short direct repeats and an overlap of 3 bases. As this is the first breakpoint resulting in the apposition of inverted sequence to be analyzed at the level of DNA sequence, we speculate whether structural features described here are typical of such rearrangements. The structure observed is consistent with, but does not prove, that the sequence is the endpoint of a true inversion since only one junction has been isolated and characterized.     

Maize high mobility group proteins bind to CCAAT and TATA boxes of a zein gene promoter

A 216-base pair promoter fragment of the 19-kDa zein storage protein gene pMS1, containing the CCAAT and TATA boxes, was analyzed for its in vitro interactions with purified high mobility group (HMG) proteins from maize endosperm tissue. It was found that the HMG proteins display a preferential binding of A/T-rich DNA regions like their animal counterparts, although the A/T content seems not to be the only determinant for binding specificity. Surprisingly, a specific binding of the HMG proteins occurs at the CCAAT and the TATA boxes as indicated by footprinting experiments.