Document 0572
 DOCN  M9620572
 TI    Inefficient spliceosome assembly and abnormal branch site selection in
       splicing of an HIV-1 transcript in vitro.
 DT    9602
 AU    Dyhr-Mikkelsen H; Kjems J; Department of Molecular Biology, University
       of Aarhus, Denmark.
 SO    J Biol Chem. 1995 Oct 13;270(41):24060-6. Unique Identifier : AIDSLINE
       MED/96025786
 AB    Continuous replication of human immunodeficiency virus type I (HIV-1)
       requires balanced expression of spliced and nonspliced mRNAs in the
       cytoplasm. This process is regulated post-transcriptionally by the
       viral-encoded Rev protein. An important prerequisite for Rev
       responsiveness is the presence of weak splice sites in the viral mRNA.
       We have investigated the splicing of the second intron of the HIV-1
       Tat/Rev transcript in vitro and show that the 3'-splice site region is
       responsible for the inefficient splicing of the HIV-1 transcript. In
       contrast, the HIV-1 5'-splice site is highly functional in combination
       with a heterologous 3'-splice site. Incubation of the HIV-1 transcript
       in nuclear extract leads to a rapid accumulation of 50 S nonproductive
       pre-spliceosome complexes. These complexes contain mainly U1 and U2
       small nuclear ribonucleoproteins and are formed independently of the
       presence of the downstream 3'-splice site. The HIV-1 transcripts, which
       do proceed through the first splicing step, utilize primarily a uridine
       as the branch acceptor nucleotide. Sequence comparison with other HIV-1
       introns suggests that nucleotides other than adenosines are commonly
       used as branch points in these viruses.
 DE    Base Sequence  Blotting, Northern  DNA Primers  Gene Products,
       rev/*BIOSYNTHESIS  Gene Products, tat/BIOSYNTHESIS  Human
       HIV-1/*GENETICS/*METABOLISM  Molecular Sequence Data  Plasmids
       Restriction Mapping  Ribonucleoproteins, Small Nuclear/METABOLISM  RNA
       Precursors/*METABOLISM  *RNA Splicing  RNA, Messenger/*BIOSYNTHESIS
       RNA, Small Nuclear/BIOSYNTHESIS  Spliceosomes/*METABOLISM  Support,
       Non-U.S. Gov't  *Transcription, Genetic  JOURNAL ARTICLE

       SOURCE: National Library of Medicine.  NOTICE: This material may be
       protected by Copyright Law (Title 17, U.S.Code).