Q14978

Nopp140, previously named p130, is a nucleolar phosphoprotein that has been shown to exist in multiple forms with different sizes. Nopp140 functions both as a chaperone for import and/or export from the nucleolus and as a transcription factor. Nopp140 was originally identified from rat liver as an NLS (nuclear localization signal)-binding protein, and has been further characterized as an RNAP (RNA Polymerase)-interacting protein. Nopp140 also associates with the general transcription factor TFIIB, and the protein kinase casein kinase II (CKII). CKII heavily phosphorylates Nopp140 to mediate binding of Nopp140 to NLS. Nopp 140 colocalizes with another nucleolar protein, NAP57, in the nucleolus and coiled bodies, and is thought to be involved in activities carried out within the nucleolus.