TRANSCRIPTION AND POLYADENYLATION IN A SHORT HUMAN INTERGENIC REGION

The poly(A) signal of the human Lamin B2 gene was previously shown to lie 600 bp upstream of the cap site of a gene of unknown function (ppv 1). However, using RNase protection analysis, we show that ppv1 has tw o clusters of multiple initiation sites, so that the 5' cap site lies only similar to 280 nt downstream of the Lamin B2 poly(A) signal. We a nalysed nascent transcription across this unusually short intergenic r egion using nuclear run-on analysis of both the endogenous locus and o f transiently transfected hybrid constructs. Surprisingly, transcripti on of the Lamin B2 gene does not appear to terminate prior to any of t he mapped ppv1 start sites, although pausing of the elongating polymer ase complexes is observed downstream of the Lamin B2 poly(A) signal. W e suggest that this pausing may be sufficient to protect the downstrea m gene from transcriptional interference. Finally, we have also invest igated the sequences required for efficient recognition of the Lamin B 2 poly(A) signal. We show that sequences upstream of the AAUAAA elemen t are required for full activity, which is an unusual feature of mamma lian poly(A) signals.