title: Specificity of the methylation-suppressed A isoform of candidate tumor suppressor RASSF1 for microtubule hyperstabilization is determined by cell death inducer C19ORF5.
abstract: Isoform-specific epigenetic silencing of RASSF1A (3p21.3) by promoter-specific CpG island hypermethylation occurs at high frequency in human tumors, whereas the closely related product of the same gene, RASSF1C, continues to be expressed. Both isoforms in isolation exhibit tumor suppressor properties and we show here similar cellular locations on mitochondria and microtubules, paclitaxel-like microtubule hyperstabilization, disruption of mitosis, and interaction with C19ORF5. We show both have identical but distinct sequence domains for microtubule association and hyperstabilization. C19ORF5 is a hyperstabilized microtubule-specific binding protein of which accumulation causes mitochondrial aggregation and cell death. We report herein that when A or C isoforms of RASSF1 are coexpressed with C19ORF5, the unique N-terminal sequence of RASSF1C prevents it from hyperstabilizing microtubules. This confers specificity on RASSF1A in microtubule hyperstabilization and accumulation of C19ORF5 on microtubules and could underlie a specific effect of hypermethylation-suppressed RASSF1A in tumor suppression.
authors.affiliation: Center for Cancer Biology and Nutrition, Institute of Biosciences and Technology, Texas A&M University System Health Science Center, Houston, Texas 77030, USA.
authors.forename: Leyuan
authors.initials: L
authors.lastname: Liu
authors.forename: Amy
authors.initials: A
authors.lastname: Vo
authors.forename: Wallace L
authors.initials: WL
authors.lastname: McKeehan
mesh_terms: D000595:Amino Acid Sequence; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D016923:Cell Death; D019175:DNA Methylation; D015536:Down-Regulation; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D016147:Genes, Tumor Suppressor; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D017239:Paclitaxel / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics*; D020033:Protein Isoforms; D013347:Subcellular Fractions; D013379:Substrate Specificity; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D000972:Antineoplastic Agents, Phytogenic; C475491:MAP1B protein, human; D008869:Microtubule-Associated Proteins; D009419:Nerve Tissue Proteins; D020033:Protein Isoforms; C411762:RASSF1 protein, human; D025521:Tumor Suppressor Proteins; D017239:Paclitaxel