Nucleic Acids Research, Vol 24, Issue 11 2073-2079, Copyright © 1996 by Oxford University Press
AR Ellison and JO Bishop
When employed as a transgene reporter, the herpes simplex type 1 virus
(HSV1) thymidine kinase gene (tk) is ectopically expressed in mouse testis.
The principal testicular mRNA lacks the 5'-end of the tk reading frame. As
a result the principal translation products, P2 and P3, are N-terminally
truncated. These co-migrate in SDS-PAGE with polypeptides synthesised
during HSV1 infection that were previously thought to be initiated at
methionine codons ATG46 and ATG60. Prompted by these observations we
generated modified tk genes each carrying only one of the first three ATG
codons. Transfected cells expressed both full-length enzyme (P1) and P2
when only ATG1 was unmodified, P2 and P3 when only ATG46 was unmodified or
P2 and a fourth polypeptide (P4) when only ATG60 was unmodified. Our
observations indicate that P3 is initiated at ATG46 rather than ATG60,
while P2 is initiated at a non- ATG codon rather than ATG46 and P4 is
initiated at ATG60. When either of two putative non-ATG initiation codons
was modified P2 was no longer produced. Cells mainly expressing either P1
or P3 exhibited the same sensitivity to Ganciclovir as cells transfected
with the unaltered tk gene. P1 and P3 both have TK activity while P4
probably has none.
ARTICLES
Initiation of herpes simplex virus thymidine kinase polypeptides
Centre for Genome Research, University of Edinburgh, UK.
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