Mapping of the human autoantigen pericentriolar material 1 (PCM1) gene to chromosome 8p21.3-p22

Zika virus increases mind bomb 1 levels, causing degradation of pericentriolar material 1 (PCM1) and dispersion of PCM1-containing granules from the centrosome

The centrosome is a cytoplasmic nonenveloped organelle functioning as one of the microtubule-organizing centers and composing a centriole center surrounded by pericentriolar material (PCM) granules. PCM consists of many centrosomal proteins, including PCM1 and centrosomal protein 131 (CEP131), and helps maintain centrosome stability. Zika virus (ZIKV) is a flavivirus of the family Flaviviridae whose RNA and viral particles are replicated in the cytoplasm. However, how ZIKV interacts with host cell components during its productive infection stage is incompletely understood. Here, using several primate cell lines, we report that ZIKV infection disrupts and disperses the PCM granules. We demonstrate that PCM1- and CEP131-containing granules are dispersed in ZIKV-infected cells, whereas the centrioles remain intact. We found that ZIKV does not significantly alter cellular skeletal proteins, and, hence, these proteins may not be involved in the interaction between ZIKV and centrosomal proteins. Moreover, ZIKV infection decreased PCM1 and CEP131 protein, but not mRNA, levels. We further found that the protease inhibitor MG132 prevents the decrease in PCM1 and CEP131 levels and centriolar satellite dispersion. Therefore, we hypothesized that ZIKV infection induces proteasomal PCM1 and CEP131 degradation and thereby disrupts the PCM granules. Supporting this hypothesis, we show that ZIKV infection increases levels of mind bomb 1 (MIB1), previously demonstrated to be an E3 ubiquitin ligase for PCM1 and CEP131 and that ZIKV fails to degrade or disperse PCM in MIB1-ko cells. Our results imply that ZIKV infection activates MIB1-mediated ubiquitination that degrades PCM1 and CEP131, leading to PCM granule dispersion.

RET/PCM-1: a novel fusion gene in papillary thyroid carcinoma

The RET proto-oncogene is often activated through somatic rearrangements in papillary thyroid carcinomas (PTCs). Three main rearranged forms of RET have been described: RET/PTC1 and RET/PTC3, which arise from a paracentric inversion and RET/PTC2, which originates from a 10 : 17 translocation. We previously developed a dual-color FISH test to detect these RET rearrangements in interphase nuclei of thyroid lesions. This approach allowed us to detect a novel translocation involving the RET region, which was not detectable by RT - PCR with specific primers for known rearrangements. A combination of RT - PCR and RACE analyses finally led to the identification of the fusion gene, which involves the 5' portion of PCM-1, a gene coding for a centrosomal protein with distinct cell cycle distribution, and the RET tyrosine kinase (TK) domain. FISH analysis confirmed the chromosomal localization of PCM-1 on chromosome 8p21-22, a region commonly deleted in several tumors. Immunohistochemistry, using an antibody specific for the C-terminal portion of PCM-1 showed that the protein level is drastically decreased and its subcellular localization is altered in thyroid tumor tissue with respect to normal thyroid. However, heterozygosity is retained for seven microsatellite markers in the 8p21-22 region, suggesting that the non-rearranged PCM-1 allele is not lost and that the translocation is balanced. Oncogene (2000) 19, 4236 - 4242

High-resolution physical map and transcript identification of a prostate cancer deletion interval on 8p22

A genomic interval of approximately 1-1.5 Mb centered at the MSR marker on 8p22 has emerged as a possible site for a tumor suppressor gene, based on high rates of allele loss and the presence of a homozygous deletion found in metastatic prostate cancer. The objective of this study was to prepare a bacterial contig of this interval, integrate the contig with radiation hybrid (RH) databases, and use these resources to identify transcription units that might represent the candidate tumor suppressor genes. Here we present a complete bacterial contig across the interval, which was assembled using 22 published and 17 newly originated STSs. The physical map provides twofold or greater coverage over much of the interval, including 17 BACs, 15 P1s, 2 cosmids, and 1 PAC clone. The position of the selected markers across the interval in relation to the other markers on the larger chromosomal scale was confirmed by RH mapping using the Stanford G3 RH panel. Transcribed units within the deletion region were identified by exon amplification, searching of the Human Transcript Map, placement of unmapped expressed sequence tags (ESTs) from the Radiation Hybrid Database (RHdb), and from other published sources, resulting in the isolation of six unique expressed sequences. The transcript map of the deletion interval now includes two known genes (MSR and N33) and six novel ESTs.

Localization of autoepitopes on the PCM-1 autoantigen using scleroderma sera with autoantibodies against the centrosome

Characterization of epitope domains of autoantigens is important for deducing the cellular functions of autoantigens and may be important for understanding the autoimmune response. In the reported studies, epitope analysis of the centrosome autoantigen PCM-1 was performed. For these investigations, portion of the PCM-1 cDNA were subcloned into the pMAL expression plasmid, fusion proteins were induced, and aliquots of the extracts were probed by immunoblot analysis using two human autoimmune anticentrosome autoantisera. Immunoblotting identified three individual autoepitopes of 26-40 amino acid residues, amino acids 506-545, 1434-1465, and 1661-1686, within the PCM-1 protein. ELISA assays using non-denatured proteins did not identity any additional autoepitopes in the remainder of the PCM-1 molecule. To analyze the identified autoepitopes further, synthetic peptides were generated that covered each of the three autoepitopes and the synthetic peptides then were probed using the scleroderma sera. Peptides that covered the antigenic regions from amino acids 506-545 and 1434-1465 failed to react with the anticentrosome autoantisera suggesting that overall protein conformation may be important for the formation of those two autoepitopes. Peptides derived from the sequence of the third autoepitope were recognized by autoantibodies present in the anticentrosome autoantisera allowing the identification of the tripeptide KDC as the autoepitope in this region of the PCM-1 molecule. These studies lay the foundation for future investigations of the autoimmune response in scleroderma patients that are producing anticentrosome autoantibodies and should allow an investigation of the cellular role of the PCM-1 protein.

The centrosome in animal cells and its functional homologs in plant and yeast cells

The centrosome is the principal microtubule-organizing center in mammalian cells. Until recently, the centrosome could only be studied at the ultrastructural level and defined as a functional entity. However, during the past decade a number of clever experimental strategies have been used to identify numerous molecular components of the centrosome. The identification of biochemical subunits of the centrosome complex has allowed the centrosome to be investigated in much more detail, resulting in important advances being made in our understanding of microtubule nucleation events, spindle formation, the assembly and replication of the centrosome, and the nature of the microtubule-organizing centers in plant cells and lower eukaryotes. The next several years should see additional rapid progress in our understanding of the microtubule cytoskeleton as investigators begin to assign functions to the centrosome proteins that have already been reported and as additional centrosome components are discovered.

Autoepitope mapping of the centrosome autoantigen PCM-1 using scleroderma sera with anticentrosome autoantibodies

We previously characterized a scleroderma serum (serum 1) containing autoantibodies against centrosome autoantigens that have been named PCM-1, PCM-2 and PCM-3. In this study, we analyzed another scleroderma serum (serum 2) reactive with centrosome autoantigens of identical molecular weights to those recognized by serum 1. To further analyze the autoepitope domains in PCM-1 recognized by the autoantibodies present in scleroderma sera, cDNAs encoding different portions of the PCM-1 autoantigen were expressed in bacteria as fusion proteins. The immunoreactivity of the fusion proteins to the scleroderma sera was assayed by immunoblot analysis. Two regions containing autoepitope domains reactive with both sera were identified in the PCM-1 molecule. One is between amino acids 312-706 of the PCM-1 autoantigen, and the other is localized between amino acids 1,433-1,787, indicating that the immune response is oligoclonal. The results are important to clarify the mechanism of induction of anticentrosome autoantibodies. The potential diagnostic and prognostic significance of the autoantibodies for subgroups of scleroderma is discussed.