Stress-induced nuclear bodies are sites of accumulation of pre-mRNA processing factors

Heterogeneous nuclear ribonucleoprotein (hnRNP) HAP (hnRNP A1 interacting p rotein) is a multifunctional protein with roles in RNA metabolism, transcri ption, and nuclear structure. After stress treatments, HAP is recruited to a small number of nuclear bodies, usually adjacent to the nucleoli, which c onsist of clusters of perichromatin granules and are depots of transcripts synthesized before stress. In this article we show that HAP bodies are site s of accumulation for a subset of RNA processing factors and are related to Sam68 nuclear bodies (SNBs) detectable in unstressed cells. Indeed, HAP an d Sam68 are both present in SNBs and in HAP bodies, that we rename "stress- induced SNBs." The determinants required for the redistribution of HAP lie between residue 580 and 788. Different portions of this region direct the r ecruitment of the green fluorescent protein to stress-induced SNBs, suggest ing an interaction of HAP with different components of the bodies. With the use of the 580-725 region as bait in a two-hybrid screening, we have selec ted SRp30c and 9G8, two members of the SR family of splicing factors. Splic ing factors are differentially affected by heat shock: SRp30c and SF2/ASF a re efficiently recruited to stress-induced SNBs, whereas the distribution o f SC35 is not perturbed. We propose that the differential sequestration of splicing factors could affect processing of specific transcripts. According ly, the formation of stress-induced SNBs is accompanied by a change in the splicing pattern of the adenovirus E1A transcripts.