Paraspeckle Component 1 (PSPC1)

PSP1-beta contains 393 amino acids and is identical to PSP1-alpha for the first 386 amino acids. Both PSP1 isoforms have 2 RNA-binding domains in their N-terminal halves. Northern blot analysis detected ubiquitous expression of at least 2 PSP1 transcripts of about 2.5 kb. Both PSP1 isoforms colocalized with p54NRB (NONO) and PSP2 (RBM14) in nucleoplasmic structures called paraspeckles, which were adjacent to but distinct from SC35 (SFRS2)-containing splicing speckles.

Mutation analysis showed that targeting of PSP1 to paraspeckles required either of its RNA-binding domains and its C-terminal coiled-coil domain, whereas accumulation of PSP1 at perinucleolar caps and its interaction with p54NRB required only the C-terminal coiled-coil domain.