Figure 1

Model for HTLV-1 p30^II transcriptional and posttranscriptional gene regulation. The cell nucleus surrounded by the nuclear membrane and key components are shown. p30^II can directly interact with CBP/p300 and modulate transcription of viral and/or cellular genes. At low concentration p30^II may stabilize the transcription complex and potentiate transcription, whereas a high concentration it may compete for limited amounts of CBP/p300 and repress gene expression. p30^II (as well as the homologous p28^II of HTLV-2) specifically binds tax/rex mRNA and block its export, reducing Tax and Rex and ultimately repressing viral gene expression. This interaction may be directly linked to splicing factors and splicing and/or the juxtaposition of specific exon/exon junction sequences. Thus, p30^II is a multifunctional protein with transcriptional and post-transcriptional roles in regulating viral and/or cellular gene expression.