Effects of translation initiation factor eIF-5A on the functioning of human T-cell leukemia virus type I Rex and human immunodeficiency virus Rev inhibited trans dominantly by a Rex mutant deficient in RNA binding.
The viral transactivator proteins Rex and Rev are necessary for the expression of structural proteins of human T-cell leukemia virus type I and human immunodeficiency virus type 1, respectively. Although the interaction of Rex/Rev with a cellular cofactor(s) has been thought to be required for Rex/Rev action, there is no suitable system to search for the cofactor(s) in mammalian cells. We found that a Rex mutant, TAgRex, which contains a simian virus 40 nuclear localization signal in place of the N-terminal 19 amino acids of Rex, could dominantly inhibit wild-type Rex/Rev functions. The inhibition did not require either Rev response element/Rex response element binding or the oligomerization ability of the mutant, but it did require a region around amino acid 90 of the Rex protein, suggesting that TAgRex sequestered the cellular cofactor. Complementation with the eukaryotic translation initiation factor 5A (eIF-5A) in this system could restore the impaired Rex function. These results indicate that eIF-5A is the cofactor indispensable for Rex function. Additionally, by using a two-hybrid system, the homo-oligomer formation of Rex was found to be mediated by the region around amino acid 90 in addition to Tyr-64 and Trp-65 of Rex protein. Thus, eIF-5A may play a part in the formation of the Rex homo-oligomer.
Katahira
J
J
Institute for Virus Research, Kyoto University, Japan.
Ishizaki
T
T
Sakai
H
H
Adachi
A
A
Yamamoto
K
K
Shida
H
H
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers / Q000235:genetics; D004279:DNA, Viral / Q000235:genetics; D015694:Gene Products, rev / Q000235:genetics* / Q000378:metabolism*; D016370:Gene Products, rex / Q000235:genetics* / Q000378:metabolism*; D005799:Genes, Dominant; D015497:HIV-1 / Q000235:genetics* / Q000378:metabolism*; D015368:Human T-lymphotropic virus 1 / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D010448:Peptide Initiation Factors / Q000378:metabolism*; D012367:RNA, Viral / Q000378:metabolism; D016601:RNA-Binding Proteins; D054321:rev Gene Products, Human Immunodeficiency Virus; D000097574:Eukaryotic Translation Initiation Factor 5A
D017931:DNA Primers; D004279:DNA, Viral; D015694:Gene Products, rev; D016370:Gene Products, rex; D010448:Peptide Initiation Factors; D012367:RNA, Viral; D016601:RNA-Binding Proteins; D054321:rev Gene Products, Human Immunodeficiency Virus; D000097574:Eukaryotic Translation Initiation Factor 5A