Spliced human endogenous retroviral HERV-H env transcripts in T-cell leukaemia cell lines and normal leukocytes: alternative splicing pattern of HERV-H transcripts.
The majority of human endogenous retroviral HERV-H elements in the human genome have large deletions in pol and lack most of env, 5-10% are more or less complete with a potentially immunosuppressive transmembrane protein-encoding env region. Spliced HERV-H env transcripts were detected in T-cell leukaemia cell lines and lymphocytes from healthy blood donors by using RT-PCR. The transcripts all contained a splice donor in the leader region downstream from the primer-binding site and a previously unreported splice acceptor in the integrase-encoding region of pol, absent in the HERV-H deletion elements. In singly spliced transcripts the leader and integrase regions were joined directly whereas in multiply spliced transcripts they were joined with an alternative exon from the protease-encoding region located between the two regions. env transcripts from three different HERV-H elements were identified: one element similar to a HERV-H consensus sequence was primarily amplified from the T-cell leukaemia cell lines and two other more defective elements were amplified from normal lymphocytes. One of these elements was shown to be a reintegrated spliced transcript where the protease and integrase regions were joined, removing most of pol but leaving gag intact. Other spliced transcripts, joining the protease region and the 3'-LTR, were also amplified. The fact that HERV-H elements with an intact env splice acceptor also use the splice sites in the protease-encoding region suggests that this unusual multiple splice pattern could have a biological function in the intact HERV-H.
Lindeskog
M
M
Department of Medical Microbiology, Lund University, Sweden. mats.lindeskog@mmb.lu.se
Blomberg
J
J
D017398:Alternative Splicing; D001483:Base Sequence; D010450:Endopeptidases / Q000235:genetics; D015967:Gene Expression Regulation, Viral; D015686:Gene Products, env / Q000235:genetics*; D015752:Genes, env; D006801:Humans; D015458:Leukemia, T-Cell / Q000821:virology*; D008214:Lymphocytes / Q000821:virology*; D008969:Molecular Sequence Data; D011533:Proviruses / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid; D012190:Retroviridae / Q000235:genetics*; D016415:Sequence Alignment
D015686:Gene Products, env; D012333:RNA, Messenger; D012367:RNA, Viral; D010450:Endopeptidases