Internal promoter elements of transfer RNA genes are preferentially exposed in chromatin.

We have examined the chromatin organization of a cluster of transfer RNA genes at the cytogenic locus 90BC on the right arm of the third Drosophila melanogaster chromosome. We find that the internal promoter sequences are preferentially exposed to micrococcal nuclease and DNase I in chromatin. Moreover, these exposed sequences have an unusual single strand nuclease-sensitive conformation.