Specific interaction with the nuclear transporter importin ?2 can modulate paraspeckle protein 1 delivery to nuclear paraspeckles.

ABSTRACT: Importin (IMP) superfamily members mediate regulated nucleocytoplasmic transport, which is central to key cellular processes. Although individual IMP? proteins exhibit dynamic synthesis and subcellular localization during cellular differentiation, including during spermatogenesis, little is known of how this affects cell fate. To investigate how IMP?s control cellular development, we conducted a yeast two-hybrid screen for IMP?2 cargoes in embryonic day 12.5 mouse testis, a site of peak IMP?2 expression coincident with germ-line masculization. We identified paraspeckle protein 1 (PSPC1), the original defining component of nuclear paraspeckles, as an IMP?2-binding partner. PSPC1-IMP?2 binding in testis was confirmed in immunoprecipitations and pull downs, and an enzyme-linked immunosorbent assay-based assay demonstrated direct, high-affinity PSPC1 binding to either IMP?2/IMP?1 or IMP?6/IMP?1. Coexpression of full-length PSPC1 and IMP?2 in HeLa cells yielded increased PSPC1 localization in nuclear paraspeckles. High-throughput image analysis of >3500 cells indicated IMP?2 levels can directly determine PSPC1-positive nuclear speckle numbers and size; a transport-deficient IMP?2 isoform or small interfering RNA knockdown of IMP?2 each reduced endogenous PSPC1 accumulation in speckles. This first validation of an IMP?2 nuclear import cargo in fetal testis provides novel evidence that PSPC1 delivery to paraspeckles, and consequently paraspeckle function, may be controlled by modulated synthesis of specific IMPs.

SUBMITTER: Major AT 

PROVIDER: S-EPMC4395133 | biostudies-literature | 2015 Apr

REPOSITORIES: biostudies-literature