MICROINJECTION OF ANTI-COILIN ANTIBODIES AFFECTS THE STRUCTURE OF COILED BODIES

The coiled body is a distinct subnuclear domain enriched in small nucl ear ribonucleoprotein particles (snRNPs) involved in processing of pre -mRNA. Although the function of the coiled body is still unknown, curr ent models propose that it may have a role in snRNP biogenesis, transp ort, or recycling. Here we describe that anti-coilin antibodies promot e a specific disappearance of the coiled body in living human cells, t hus providing a novel tool for the functional analysis of this structu re. Monoclonal antibodies (mAbs) were raised against recombinant human coilin, the major structural protein of the coiled body. Four mAbs ar e shown to induce a progressive disappearance of coiled bodies within, similar to 6 h after microinjection into the nucleus of HeLa cells. Af ter their disappearance, coiled bodies are not seen to re-form, althou gh injected cells remain viable for at least 3 d. Epitope mapping reve als that the mAbs recognize distinct amino acid motifs scattered along the complete coilin sequence. By 24 and 48 h after injection of antib odies that promote coiled body disappearance, splicing snRNPs are norm ally distributed in the nucleoplasm, the nucleolus remains unaffected, and the cell cycle progresses normally. Furthermore, cells devoid of coiled bodies for similar to 24 h maintain the ability to splice both adenoviral pre-mRNAs and transiently overexpressed human beta-globin t ranscripts. In conclusion, within the time range of this study, no maj or nuclear abnormalities are detected after coiled body disappearance.