hnRNP K binds a core polypyrimidine element in the eukaryotic translation initiation factor 4E (eIF4E) promoter, and its regulation of eIF4E contributes to neoplastic transformation.
Translation initiation factor eukaryotic translation initiation factor 4E (eIF4E) plays a key role in regulation of cellular proliferation. Its effects on the m7GpppN mRNA cap are critical because overexpression of eIF4E transforms cells, and eIF4E function is rate-limiting for G1 passage. Although we identified eIF4E as a c-Myc target, little else is known about its transcriptional regulation. Previously, we described an element at position -25 (TTACCCCCCCTT) that was critical for eIF4E promoter function. Here we report that this sequence (named 4EBE, for eIF4E basal element) functions as a basal promoter element that binds hnRNP K. The 4EBE is sufficient to replace TATA sequences in a heterologous reporter construct. Interactions between 4EBE and upstream activator sites are position, distance, and sequence dependent. Using DNA affinity chromatography, we identified hnRNP K as a 4EBE-binding protein. Chromatin immunoprecipitation, siRNA interference, and hnRNP K overexpression demonstrate that hnRNP K can regulate eIF4E mRNA. Moreover, hnRNP K increased translation initiation, increased cell division, and promoted neoplastic transformation in an eIF4E-dependent manner. hnRNP K binds the TATA-binding protein, explaining how the 4EBE might replace TATA in the eIF4E promoter. hnRNP K is an unusually diverse regulator of multiple steps in growth regulation because it also directly regulates c-myc transcription, mRNA export, splicing, and translation initiation.
Lynch
Mary
M
Cancer Research Center at Massachusetts General Hospital and Harvard Medical School, 55 Fruit St., Boston, MA 02114, USA.
Chen
Li
L
Ravitz
Michael J
MJ
Mehtani
Sapna
S
Korenblat
Kevin
K
Pazin
Michael J
MJ
Schmidt
Emmett V
EV
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002471:Cell Transformation, Neoplastic / Q000378:metabolism*; D039561:Eukaryotic Initiation Factor-4E / Q000235:genetics / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D006367:HeLa Cells; D034641:Heterogeneous-Nuclear Ribonucleoprotein K / Q000502:physiology*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000502:physiology*; D051381:Rats; D016385:TATA Box / Q000235:genetics; D014158:Transcription, Genetic / Q000502:physiology
D039561:Eukaryotic Initiation Factor-4E; D034641:Heterogeneous-Nuclear Ribonucleoprotein K