Characterization of hCINAP, a novel coilin-interacting protein by a transcript from the transcription factor TAFIID32 locus

Niovi Santama, Stephen C. Ogg, Anna Malekkou, Spyros E. Zographos, Karsten Weis, Angus I. Lamond

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Coilin is a marker protein for the Cajal body, a subnuclear domain acting as a site for assembly and maturation of nuclear RNA-protein complexes. Using a yeast two-hybrid screen to identify coilin-interactingproteins, we have identified hCINAP (human coilin interactingnuclear ATPase protein), a nuclear factor of 172 amino acids with a P-loop nucleotide binding motif and ATPase activity. The hCINAP protein sequence is highly conserved across its full-length from human to plants and yeast and is ubiquitously expressed in all human tissues and cell lines tested. The yeast orthologue of CINAP is a single copy, essential gene. Tagged hCINAP is present in complexes containing coilin in mammalian cells and recombinant, Escherichia coli expressed hCINAP binds directly to coilin in vitro. The 214 carboxyl-terminal residues of coilin appear essential for the interaction with hCINAP. Both immunofluorescence and fluorescent protein tagging show that hCINAP is specifically nuclear and distributed in a widespread, diffuse nucleoplasmic pattern, excludingnucleoli, with some concentration also in Cajal bodies. Overexpression of hCINAP in HeLa cells results in a decrease in the average number of Cajal bodies per nucleus, consistent with it affecting either the stability of Cajal bodies and/or their rate of assembly. The hCINAP mRNA is an alternatively spliced transcript from the TAF9 locus, which encodes the basal transcription factor subunit TAFIID 32. However, hCINAP and TAFIID32 mRNAs are translated from different ATG codons and use distinct reading frames, resulting in them having no identity in their respective protein sequences.

Original languageEnglish
Pages (from-to)36429-36441
Number of pages13
JournalJournal of Biological Chemistry
Volume280
Issue number43
DOIs
Publication statusPublished - 28 Oct 2005

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