title: Paired-like homeoprotein ESXR1 acts as a sequence-specific transcriptional repressor of the human K-ras gene.
abstract: Gain-of-function mutation of the K-ras gene is one of the most common genetic changes in human tumors. In tumors carrying K-ras mutation, the presence of oncogenic K-Ras is necessary for maintenance of the transformed phenotype. ESXR1 is a human paired-like homeodomain-containing protein expressed primarily in the testis. In cells, the 65-kDa full-length ESXR1 protein is proteolytically processed into an N-terminal 45-kDa fragment containing the homeodomain, which localizes exclusively within the nucleus, and a C-terminal 20-kDa fragment consisting of a proline-rich repeat region, which is located in the cytoplasm. In this work, we demonstrated that the N-terminal ESXR1 fragment specifically recognizes the TAATNNNATTA P3 consensus sequence for the paired-like homeodomain and functions as a sequence-specific transcriptional repressor. We also showed that the N-terminal ESXR1 fragment binds to the TAATGTTATTA sequence present within the first intron of the human K-ras gene and inhibits its expression at both mRNA and protein levels. Ectopic expression of the N-terminal ESXR1 fragment in human carcinoma cells that carry mutated K-ras reduces the level of K-Ras and thereby inhibits the tumor cell proliferation. Identification of ESXR1 as a transcriptional repressor of K-ras has an important implication for the development of cancer therapy that inhibits oncogenic K-Ras expression.
authors.affiliation: Division of Molecular Oncology, Institute for Genetic Medicine, Hokkaido University, Kita-ku, Sapporo, Japan.
authors.forename: Masatomo
authors.initials: M
authors.lastname: Yanagihara
authors.forename: Susumu
authors.initials: S
authors.lastname: Ishikawa
authors.forename: Masanori
authors.initials: M
authors.lastname: Naito
authors.forename: Junta
authors.initials: J
authors.lastname: Nakajima
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Aburatani
authors.forename: Masanori
authors.initials: M
authors.lastname: Hatakeyama
mesh_terms: D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002522:Chlorocebus aethiops; D015536:Down-Regulation; D024202:Electrophoretic Mobility Shift Assay; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D011905:Genes, ras / Q000235:genetics*; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D015151:Immunoblotting; D009154:Mutation; D009369:Neoplasms / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic / Q000235:genetics*
chemical_list: C432969:ESX1 protein, human; D018398:Homeodomain Proteins