title: Direct recruitment of ERK cascade components to inducible genes is regulated by heterogeneous nuclear ribonucleoprotein (hnRNP) K.
abstract: Components of the ERK cascade are recruited to genes, but it remains unknown how they are regulated at these sites. The RNA-binding protein heterogeneous nuclear ribonucleoprotein (hnRNP) K interacts with kinases and is found along genes including the mitogen-inducible early response gene EGR-1. Here, we used chromatin immunoprecipitations to study co-recruitment of hnRNP K and ERK cascade activity along the EGR-1 gene. These measurements revealed that the spatiotemporal binding patterns of ERK cascade transducers (GRB2, SOS, B-Raf, MEK, and ERK) at the EGR-1 locus resemble both hnRNP K and RNA polymerase II (Pol II). Inhibition of EGR-1 transcription with either serum-responsive factor knockdown or 5,6-dichloro-1-β-D-ribofuranosylbenzimidazole altered recruitment of all of the above ERK cascade components along this locus that mirrored the changes in Pol II and hnRNP K profiles. siRNA knockdown of hnRNP K decreased the levels of active MEK and ERK at the EGR-1, changes associated with decreased levels of elongating pre-mRNA and less efficient splicing. The hnRNP K dependence and pattern of ERK cascade activation at the c-MYC locus were different from at EGR-1. Ribonucleoprotein immunoprecipitations revealed that hnRNP K was associated with the EGR-1 but not c-MYC mRNAs. These data suggest a model where Pol II transcription-driven recruitment of hnRNP K along the EGR-1 locus compartmentalizes activation of the ERK cascade at these genes, events that regulate synthesis of mature mRNA.
authors.affiliation: Department of Medicine, University of Washington, Seattle, Washington 98109, USA.
authors.forename: Michal
authors.initials: M
authors.lastname: Mikula
authors.forename: Karol
authors.initials: K
authors.lastname: Bomsztyk
mesh_terms: D045744:Cell Line, Tumor; D051766:Early Growth Response Protein 1 / Q000096:biosynthesis; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology*; D056426:Genetic Loci / Q000502:physiology*; D034641:Heterogeneous-Nuclear Ribonucleoprotein K; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008954:Models, Biological; D012319:RNA Polymerase II / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D012261:Ribonucleoproteins / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology*
chemical_list: D051766:Early Growth Response Protein 1; D034641:Heterogeneous-Nuclear Ribonucleoprotein K; D012333:RNA, Messenger; D012261:Ribonucleoproteins; C072074:HNRNPK protein, human; D048049:Extracellular Signal-Regulated MAP Kinases; D012319:RNA Polymerase II