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J. Virol., Nov 1997, 8186-8194, Vol 71, No. 11
DJ Klumpp, F Stubenrauch and LA Laimins
In human papillomavirus type 31 (HPV-31), the E1--E4 and E5 open reading
frames are expressed from polycistronic mRNAs. The major polycistronic
mRNAs which encode E1--E4 and E5 are spliced messages which utilize a
splice acceptor at nucleotide (nt) 3295 (SPA3295). Our laboratory recently
developed a recombinant system for the synthesis of HPVs following
immortalization of primary keratinocytes with cloned HPV- 31 genomes (M. G.
Frattini et al., Proc. Natl. Acad. Sci. USA 93:3062- 3067, 1996). These
immortalized cell lines are capable of maintaining HPV-31 DNA as episomes
and induce the synthesis of virions in organotypic raft culture. In this
study, we used these methods to begin an analysis of the roles of E1--E4
and E5 in HPV pathogenesis by mutating the major splice at nt 3295.
Mutation of SPA3295 did not significantly alter the ability of HPV-31
genomes to replicate transiently in keratinocytes, nor did the mutation
affect the immortalization potential of HPV-31. However, genomes carrying
the SPA3295 mutation were not stably maintained as viral episomes, and the
resulting immortalized keratinocyte cell line contained multiple,
integrated copies of the mutated HPV-31 DNA. Northern analysis indicated
that cell lines immortalized with the mutant HPV-31 expressed transcripts
which were similar in size and abundance to wild-type messages, including
those transcripts which rely on utilization of SPA3295. RNase protection
and reverse transcription-PCR revealed that mutation of SPA3295 resulted in
the utilization of a cryptic splice acceptor at nt 3298. These data suggest
that the requirements for stable maintenance of HPV genomes are more
stringent than those for transient replication and that factors which
define these requirement rely on the major splice acceptor at nt 3295.
Copyright © 1997, American Society for Microbiology
Differential effects of the splice acceptor at nucleotide 3295 of human papillomavirus type 31 on stable and transient viral replication
Department of Microbiology-Immunology, Northwestern University Medical School, Chicago, Illinois 60611, USA.
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