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.