Growth-regulated expression and G0-specific turnover of the mRNA that encodes URH49, a mammalian DExH/D box protein that is highly related to the mRNA export protein UAP56.
URH49 is a mammalian protein that is 90% identical to the DExH/D box protein UAP56, an RNA helicase that is important for splicing and nuclear export of mRNA. Although Saccharomyces cerevisiae and Drosophila express only a single protein corresponding to UAP56, mRNAs encoding URH49 and UAP56 are both expressed in human and mouse cells. Both proteins interact with the mRNA export factor Aly and both are able to rescue the loss of Sub2p (the yeast homolog of UAP56), indicating that both proteins have similar functions. UAP56 mRNA is more abundant than URH49 mRNA in many tissues, although in testes URH49 mRNA is much more abundant. UAP56 and URH49 mRNAs are present at similar levels in proliferating cultured cells. However, when the cells enter quiescence, the URH49 mRNA level decreases 3-6-fold while the UAP56 mRNA level remains relatively constant. The amount of URH49 mRNA increases to the level found in proliferating cells within 5 h when quiescent cells are growth-stimulated or when protein synthesis is inhibited. URH49 mRNA is relatively unstable (T(1/2) = 4 h) in quiescent cells, but is stabilized immediately following growth stimulation or inhibition of protein synthesis. In contrast, there is much less change in the content or stability of UAP56 mRNA following growth stimulation. Our observations suggest that in mammalian cells, two UAP56-like RNA helicases are involved in splicing and nuclear export of mRNA. Differential expression of these helicases may lead to quantitative or qualitative changes in mRNA expression.
Pryor
Anne
A
The Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA.
Tung
Luh
L
Yang
Zhe
Z
Kapadia
Fehmida
F
Chang
Tien-Hsien
TH
Johnson
Lee F
LF
D018528:ATP-Binding Cassette Transporters; D021581:Active Transport, Cell Nucleus; D000251:Adenosine Triphosphatases / Q000235:genetics; D000818:Animals; D002455:Cell Division; D002467:Cell Nucleus / Q000378:metabolism; D017124:Conserved Sequence; D053487:DEAD-box RNA Helicases; D005786:Gene Expression Regulation; D005816:Genetic Complementation Test; D006367:HeLa Cells; D006801:Humans; D008297:Male; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism; D020365:RNA Helicases / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D020871:RNA Stability; D012333:RNA, Messenger / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism; D016192:Resting Phase, Cell Cycle; D014157:Transcription Factors / Q000378:metabolism
C105242:ALYREF protein, human; D018528:ATP-Binding Cassette Transporters; D009687:Nuclear Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C486334:Refbp1 protein, mouse; D014157:Transcription Factors; D000251:Adenosine Triphosphatases; C498428:DDX39A protein, human; C487886:DDX39B protein, human; C027900:RNA-dependent ATPase; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases