Role of polypyrimidine tract binding protein in the function of the hepatitis B virus posttranscriptional regulatory element.
The hepatitis B virus posttranscriptional regulatory element (PRE) is an RNA element that increases the expression of unspliced mRNAs, apparently by facilitating their export from the nucleus. We have identified a cellular protein that binds to the PRE as the polypyrimidine tract binding protein (PTB), which shuttles rapidly between the nucleus and the cytoplasm. Mutants of the PRE with mutations in PTB binding sites show markedly decreased activity, while cells that stably overexpress PTB show increased PRE-dependent gene expression. Export of PTB from the nucleus, like PRE function, is blocked by a mutant form of Ran binding protein 1 but not by leptomycin B. Therefore, PTB is important for PRE activity and appears to function as an export factor for PRE-containing mRNAs.
Zang
W Q
WQ
Department of Pathology, VA Medical Center 113B, University of California School of Medicine, San Francisco, 94121, USA.
Li
B
B
Huang
P Y
PY
Lai
M M
MM
Yen
T S
TS
D001483:Base Sequence; D001665:Binding Sites; D002467:Cell Nucleus / Q000378:metabolism*; D006515:Hepatitis B virus / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D038941:Polypyrimidine Tract-Binding Protein; D012322:RNA Precursors / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012367:RNA, Viral / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000502:physiology*; D012261:Ribonucleoproteins / Q000502:physiology*; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
D012322:RNA Precursors; D012333:RNA, Messenger; D012367:RNA, Viral; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D038941:Polypyrimidine Tract-Binding Protein