title: NORE1A, a homologue of RASSF1A tumour suppressor gene is inactivated in human cancers.
abstract: We recently demonstrated that RASSF1A, a new tumour-suppressor gene located at 3p21.3 is frequently inactivated by promoter region hypermethylation in a variety of human cancers including lung, breast, kidney and neuroblastoma. We have identified another member of the RASSF1 gene family by in silico sequence analysis using BLAST searches. NORE1 located at 1q32.1 exists in three isoforms (NORE1Aalpha, NORE1Abeta and NORE1B). Both NORE1A and NORE1B isoforms have separate CpG islands spanning their first exons. NORE1Aalpha Produces a 418 aa protein containing a Ras-association (RA) domain and a diacylglycerol (DAG) binding domain. NORE1Abeta produces a C-terminal truncation of the RA domain. NORE1B also contains the RA domain but not the DAG domain. NORE1 is the human homologue of the mouse Ras effector Nore1. No inactivating somatic mutations were found in lung tumour lines; however, NORE1A promoter region CpG island was hypermethylated in primary tumours and tumour cell lines. NORE1A promoter was methylated in 10/25 breast, 4/40 SCLC, 3/17 NSCLC, 1/6 colorectal and 3/9 kidney tumour cell lines, while NORE1B promoter was unmethylated in the same tumour cell lines. While 24% (6/25) of primary NSCLC underwent NORE1A methylation, methylation in SCLC was a rare event (0/22); (P = 0.0234). NORE1A expression in tumour cell lines was reactivated after treatment with a demethylating agent. There was no correlation between NORE1A and RASSF1A methylation status in NSCLC. Our results demonstrate that NORE1A is inactivated in a subset of human cancers by CpG island promoter hypermethylation, and in lung cancer this hypermethylation may be histological type specific.
authors.affiliation: Section of Medical and Molecular Genetics, Department of Paediatrics and Child Health, University of Birmingham, The Medical School, Edgbaston, UK.
authors.forename: Luke
authors.initials: L
authors.lastname: Hesson
authors.forename: Ashraf
authors.initials: A
authors.lastname: Dallol
authors.forename: John D
authors.initials: JD
authors.lastname: Minna
authors.forename: Eamonn R
authors.initials: ER
authors.lastname: Maher
authors.forename: Farida
authors.initials: F
authors.lastname: Latif
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D001483:Base Sequence; D019295:Computational Biology; D019175:DNA Methylation; D020868:Gene Silencing; D016147:Genes, Tumor Suppressor; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics*; D008969:Molecular Sequence Data; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics*; D009363:Neoplasm Proteins / Q000235:genetics; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000235:genetics; D017422:Sequence Analysis, DNA; D025521:Tumor Suppressor Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D009363:Neoplasm Proteins; D020033:Protein Isoforms; C411762:RASSF1 protein, human; C454042:RASSF5 protein, human; D025521:Tumor Suppressor Proteins; D020559:Monomeric GTP-Binding Proteins