Mouse Anti Human gemin5 Hybridoma [HFN6S(7H6)]

Hoyeraal-Hreidarsson syndrome (HHS) is a severe form of Dyskeratosis congenita characterized by developmental defects, bone marrow failure and immunodeficiency and has been associated with telomere dysfunction. Recently, mutations in Regulator of Telomere ELongation helicase 1 (RTEL1), a helicase first identified in Mus musculus as being responsible for the maintenance of long telomeres, have been identified in several HHS patients. Here we show that RTEL1 is required for the export and the correct cytoplasmic trafficking of the small nuclear (sn) RNA pre-U2, a component of the major spliceosome complex. RTEL1-HHS cells show abnormal subcellular partitioning of pre-U2, defects in the recycling of ribonucleotide proteins (RNP) in the cytoplasm and splicing defects. While most of these phenotypes can be suppressed by re-expressing the wild-type protein in RTEL1-HHS cells, expression of RTEL1 mutated variants in immortalized cells provokes cytoplasmic mislocalizations of pre-U2 and other RNP components, as well as splicing defects, thus phenocopying RTEL1-HHS cellular defects. Strikingly, expression of a cytoplasmic form of RTEL1 is sufficient to correct RNP mislocalizations both in RTEL1-HHS cells and in cells expressing nuclear mutated forms of RTEL1. This work unravels completely unanticipated roles for RTEL1 in RNP trafficking and strongly suggests that defects in RNP biogenesis pathways contribute to the pathology of HHS.

Spinal muscular atrophy (SMA) is a neurodegenerative disease characterized by loss of spinal motor neurons. The gene encoding the survival of motor neurons (SMN) protein is mutated in > 95% of SMA cases. SMN is the central component of a large oligomeric complex, including Gemins2-7, that is necessary and sufficient for the in vivo assembly of Sm proteins onto the small nuclear (sn)RNAs that mediate pre-mRNA splicing. After cytoplasmic assembly of the Sm core, both SMN and splicing snRNPs are imported into the nucleus, accumulating in Cajal bodies for additional snRNA maturation steps before targeting to splicing factor compartments known as "speckles." In this study, we analyzed the function of individual SMN complex members by RNA interference (RNAi). RNAi-mediated knockdown of SMN, Gemin2, Gemin3, and Gemin4 each disrupted Sm core assembly, whereas knockdown of Gemin5 and Snurportin1 had no effect. Assembly activity was rescued by expression of a GFP-SMN construct that is refractive to RNAi but not by similar constructs that contain SMA patient-derived mutations. Our results also demonstrate that Cajal body homeostasis requires SMN and ongoing snRNP biogenesis. Perturbation of SMN function results in disassembly of Cajal bodies and relocalization of the marker protein, coilin, to nucleoli. Moreover, in SMN-deficient cells, newly synthesized SmB proteins fail to associate with U2 snRNA or accumulate in Cajal bodies. Collectively, our results identify a previously uncharacterized function for Gemin3 and Gemin4 in Sm core assembly and correlate the activity of this pathway with SMA.