Heterogeneous nuclear ribonucleoprotein A1

Heterogeneous nuclear ribonucleoprotein A1 is a is_associated_with::protein that in humans is encoded by the HNRNPA1 is_associated_with::gene. Mutations in HNRNPA1 are causative of the syndrome is_associated_with::multisystem proteinopathy.

Function
This gene belongs to the A/B 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 has two repeats of quasi-RRM domains that bind to RNAs. It is one of the most abundant core proteins of hnRNP complexes and it is localized to the nucleoplasm. This protein, along with other hnRNP proteins, is exported from the nucleus, probably bound to mRNA, and is immediately re-imported. Its M9 domain acts as both a nuclear localization and nuclear export signal. The encoded protein is involved in the packaging of pre-mRNA into hnRNP particles, transport of poly A+ mRNA from the nucleus to the cytoplasm, and may modulate splice site selection. Multiple alternatively spliced transcript variants have been found for this gene but only two transcripts are fully described. These variants have multiple alternative transcription initiation sites and multiple polyA sites.

Interactions
Heterogeneous nuclear ribonucleoprotein A1 has been shown to interact with is_associated_with::BAT2, is_associated_with::Flap structure-specific endonuclease 1 and is_associated_with::IκBα.

Role in disease
Mutations in hnRNP A1 are a rare cause of multisystem proteinopathy is_associated_with::multisystem proteinopathy and ALS.