daceh at shrike.und.ac.za
Thu Jun 15 07:48:17 EST 1995
In the absence of a seemingly appropriate newsgroup I thought I'd post
this question here.
The paper `A TBP-TAF complex required for transcription of human
snRNA genes by RNA polymerases II and III' by R. William Henry et al.
in Nature 374, 13 April 1995 refers.
The above paper is the focus of a piece of work my class is doing in which
we are asked (amongst other things) what `cryptic promotors' and `basal
promotor elements' are. The context is roughly this:
The authors isolated a new regulatory complex required for the transcription
of snRNA genes. Its affinity for PSE (the basal promotor element in question)
was assessed by various means, and the neccessity of the complex for
normal expression of the U1 snRNA was also checked. Here's the rub:
A gel (fig 1c for those who have the paper) is shown of the products of
an in vitro transcription assay of SNAPc depleted nuclear extracts
complemented with various density gradient fractions, a few of which
contain the regulatory complex in question. Of course, only those
show a band corresponding to U1 transcription, but all lanes show another
band attributed by the authors to `RNAs initiated at cryptic promoters
within vector sequences'.
Could anyone clarify what this means? My guess is that it implies
the presence of sequences within the cloning vector which act as
promotors without them necessarily being intended as such - so nonspecific
transcription just happens with or without the regulatory complex.
Would I be correct here? Any helpful responses will of course be
appropriately referenced when the work is handed in.
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