HNRNPK

This gene belongs to the subfamily of ubiquitously expressed heterogeneous nuclear ribonucleoproteins (hnRNPs). The hnRNPs are RNA binding proteins and they complex with heterogeneous nuclear RNA (hnRNA). These proteins are associated with pre-mRNAs in the nucleus and appear to influence pre-mRNA processing and other aspects of mRNA metabolism and transport. While all of the hnRNPs are present in the nucleus, some seem to shuttle between the nucleus and the cytoplasm. The hnRNP proteins have distinct nucleic acid binding properties. The protein encoded by this gene is located in the nucleoplasm and has three repeats of KH domains that binds to RNAs. It is distinct among other hnRNP proteins in its binding preference; it binds tenaciously to poly(C). This protein is also thought to have a role during cell cycle progession. Several alternatively spliced transcript variants have been described for this gene, however, not all of them are fully characterized.

Full Name

heterogeneous nuclear ribonucleoprotein K

Function

One of the major pre-mRNA-binding proteins. Binds tenaciously to poly(C) sequences. Likely to play a role in the nuclear metabolism of hnRNAs, particularly for pre-mRNAs that contain cytidine-rich sequences. Can also bind poly(C) single-stranded DNA. Plays an important role in p53/TP53 response to DNA damage, acting at the level of both transcription activation and repression. When sumoylated, acts as a transcriptional coactivator of p53/TP53, playing a role in p21/CDKN1A and 14-3-3 sigma/SFN induction (By similarity).

As far as transcription repression is concerned, acts by interacting with long intergenic RNA p21 (lincRNA-p21), a non-coding RNA induced by p53/TP53. This interaction is necessary for the induction of apoptosis, but not cell cycle arrest. As part of a ribonucleoprotein complex composed at least of ZNF827, HNRNPL and the circular RNA circZNF827 that nucleates the complex on chromatin, may negatively regulate the transcription of genes involved in neuronal differentiation (PubMed:33174841).

Biological Process

mRNA splicing, via spliceosome Source: UniProtKB
Negative regulation of apoptotic process Source: MGI
Negative regulation of mRNA splicing, via spliceosome Source: Ensembl
Negative regulation of transcription, DNA-templated Source: UniProtKB
Positive regulation of low-density lipoprotein receptor activity Source: BHF-UCL
Positive regulation of receptor-mediated endocytosis Source: BHF-UCL
Positive regulation of transcription by RNA polymerase II Source: Ensembl
Regulation of gene expression Source: GO_Central
Regulation of intrinsic apoptotic signaling pathway in response to DNA damage by p53 class mediator Source: Ensembl
Regulation of low-density lipoprotein particle clearance Source: BHF-UCL
Regulation of mRNA splicing, via spliceosome Source: GO_Central
Regulation of transcription by RNA polymerase II Source: GO_Central
RNA processing Source: ProtInc
Signal transduction Source: ProtInc

Cellular Location

Nucleoplasm; Cytoplasm; Podosome. Recruited to p53/TP53-responsive promoters, in the presence of functional p53/TP53 (PubMed:16360036). In case of ASFV infection, there is a shift in the localization which becomes predominantly nuclear (PubMed:18775702).

Involvement in disease

Au-Kline syndrome (AUKS):
A disorder characterized by intellectual disability, facial dysmorphism, cardiac defects, and connective tissue and skeletal abnormalities. Dysmorphic features include long palpebral fissures, ptosis, a broad prominent nasal bridge, hypoplastic alae nasi, an open downturned mouth, ears with underdeveloped and thick helices, high palate, and a unique tongue with a prominent median crease. Hypotonia, hyporeflexia, and high pain tolerance are additional features.

PTM

Arg-296 and Arg-299 are dimethylated, probably to asymmetric dimethylarginine.
Sumoylated by CBX4. Sumoylation is increased upon DNA damage, such as that produced by doxorubicin, etoposide, UV light and camptothecin, due to enhanced CBX4 phosphorylation by HIPK2 under these conditions.
Ubiquitinated by MDM2. Doxorubicin treatment does not affect monoubiquitination, but slightly decreases HNRNPK poly-ubiquitination.
O-glycosylated (O-GlcNAcylated), in a cell cycle-dependent manner.