trans-Activation by the hnRNP K protein involves an increase in RNA synthesis from the reporter genes.
The function of many of the pre-mRNA-binding proteins in mRNA biogenesis is unclear. We have analyzed the biochemical function of the hnRNP K protein by using a mouse cDNA clone. A previous study indicated that the expression of hnRNP K activates c-myc promoter in transient transfection assays. We show that the expression of hnRNP K results in a trans-activation of a variety of RNA polymerase II promoters. The trans-activation function depends on the sequences of hnRNP K that are also necessary for RNA binding. However, the RNA binding motifs are not sufficient for trans-activation. We could identify a mutant that bound RNA in vitro but was impaired in its ability to trans-activate the reporter genes. The trans-activation was not a result of the stabilization of the reporter mRNA, because hnRNP K increased the steady-state level of the reporter mRNA without altering its decay rate. By doing nuclear run-on assays, we provide evidence that the hnRNP K protein trans-activates the reporter genes by increasing the level of transcription.
Lee
M H
MH
Department of Biochemistry, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
Mori
S
S
Raychaudhuri
P
P
D016475:3T3 Cells; D000256:Adenoviridae; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002467:Cell Nucleus / Q000378:metabolism; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis; D003001:Cloning, Molecular; D034641:Heterogeneous-Nuclear Ribonucleoprotein K; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D007700:Kinetics; D051379:Mice; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D012322:RNA Precursors / Q000378:metabolism; D012332:RNA, Heterogeneous Nuclear / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis*; D011994:Recombinant Proteins / Q000378:metabolism; D012261:Ribonucleoproteins / Q000096:biosynthesis / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection
D034641:Heterogeneous-Nuclear Ribonucleoprotein K; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D009838:Oligodeoxyribonucleotides; D012322:RNA Precursors; D012332:RNA, Heterogeneous Nuclear; D012333:RNA, Messenger; D011994:Recombinant Proteins; D012261:Ribonucleoproteins; D015500:Chloramphenicol O-Acetyltransferase