Kaposi's sarcoma-associated herpesvirus K8 exon 3 contains three 5'-splice sites and harbors a K8.1 transcription start site.
Kaposi's sarcoma-associated herpesvirus (KSHV) K8 and K8.1 open reading frames are juxtaposed and span from nucleotide (nt) 74850 to 76695 of the virus genome. A K8 pre-mRNA overlaps the entire K8.1 coding region, and alternative splicing of KSHV K8 and K8.1 pre-mRNAs each produces three isoforms (alpha, beta, and gamma) of the mRNAs. We have mapped the 5' end of the K8.1 RNA in butyrate-induced KSHV-positive JSC-1 cells to nt 75901 in the KSHV genome and have shown that exon 3 of the K8 pre-mRNA in JSC-1 cells covers most part of the intron 3 defined previously and has three 5'-splice sites (ss), respectively, at nt 75838, 76155, and 76338. Selection of the nt 75838 5'-ss dictates the K8 mRNA production and overwhelms the RNA processing. Alternative selection of other two 5'-ss is feasible and leads to production of two additional bicistronic mRNAs, K8/K8.1alpha and -beta. However, the novel bicistronic K8/K8.1 mRNAs translated a little K8 and no detectable K8.1 proteins in 293 cells. Data suggest that production of the K8/K8.1 mRNAs may be an essential way to control K8 mRNAs, especially K8alpha, to a threshold at RNA processing level.
Tang
Shuang
S
HIV and AIDS Malignancy Branch, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA.
Zheng
Zhi-Ming
ZM
D017398:Alternative Splicing; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers; D005091:Exons; D016679:Genome, Viral; D019288:Herpesvirus 8, Human / Q000235:genetics*; D006801:Humans; D007438:Introns; D016366:Open Reading Frames; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic; D014162:Transfection
D017931:DNA Primers; D012333:RNA, Messenger