title: The heterogeneous nuclear ribonucleoprotein L is an essential component in the Ca2+/calmodulin-dependent protein kinase IV-regulated alternative splicing through cytidine-adenosine repeats.
abstract: The regulation of gene expression through alternative pre-mRNA splicing is common in metazoans and is often controlled by intracellular signaling pathways that are important in cell physiology. We have shown that the alternative splicing of a number of genes is controlled by membrane depolarization and Ca2+/calmodulin-dependent protein kinase IV (CaMKIV) through CaMKIV-responsive RNA elements (CaRRE1 and CaRRE2); however, the trans-acting factors remain unknown. Here we show that the heterogeneous nuclear ribonucleoprotein (hnRNP) L is a CaRRE1 binding factor in nuclear extracts. An hnRNP L high affinity CA (cytidine-adenosine) repeat element is sufficient to mediate CaMKIV and hnRNP L repression of splicing in a location (3'-splice site proximity)-dependent way. Depletion of hnRNP L by RNA interference followed by rescue with coexpressed exogenous hnRNP L demonstrates that hnRNP L mediates the CaMKIV-regulated splicing through CA repeats in heterologous contexts. Depletion of hnRNP L also led to increased inclusion of the stress axis-regulated exon and a CA repeat-harboring exon under depolarization or with activated CaMKIV. Moreover, hnRNP L binding to CaRRE1 was increased by CaMKIV and, conversely, was reduced by pretreatments with protein phosphatases. Therefore, hnRNP L is an essential component of CaMKIV-regulated alternative splicing through CA repeats, with its phosphorylation likely playing a critical role.
authors.affiliation: Department of Physiology and Immunology, Faculty of Medicine, University of Manitoba, Winnipeg, MB R3E 0J9, Canada.
authors.forename: Jiankun
authors.initials: J
authors.lastname: Yu
authors.forename: Yan
authors.initials: Y
authors.lastname: Hai
authors.forename: Guodong
authors.initials: G
authors.lastname: Liu
authors.forename: Tielan
authors.initials: T
authors.lastname: Fang
authors.forename: Sam K P
authors.initials: SK
authors.lastname: Kung
authors.forename: Jiuyong
authors.initials: J
authors.lastname: Xie
mesh_terms: D017398:Alternative Splicing / Q000502:physiology*; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4 / Q000096:biosynthesis* / Q000235:genetics; D004789:Enzyme Activation / Q000502:physiology; D005091:Exons / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D006367:HeLa Cells; D034664:Heterogeneous-Nuclear Ribonucleoprotein L / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D010766:Phosphorylation / Q000502:physiology; D012091:Repetitive Sequences, Nucleic Acid / Q000502:physiology
chemical_list: D034664:Heterogeneous-Nuclear Ribonucleoprotein L; C517683:CAMK4 protein, human; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4