title: betaPix-b(L), a novel isoform of betaPix, is generated by alternative translation.
abstract: betaPix (Pak-interacting exchange factor) isoforms are recently identified guanine nucleotide exchange factors (GEFs) for Rho family GTPases, Rac/Cdc42, that are key players in the regulation of actin dynamics. Here we show that a novel 105-kDa betaPix isoform, betaPix-bL, is generated by alternative translation of betaPix-b mRNA. Translation of betaPix-bL starts at an atypical initiation site, GTG, that is located 57 nucleotides downstream from the newly identified 5' end of betaPix-b cDNA. The expression of two isoforms, betaPix-b and betaPix-bL, from betaPix-b mRNA is controlled by an internal ribosome entry site (IRES)-driven mechanism. Comparing to betaPix-b, betaPix-bL contains additional 105 amino acids composed of a calponin homology (CH) domain and a serine-rich sequence in the N-terminus. The expression of betaPix-bL in rat brain is developmentally regulated and high in the embryonic stages, suggesting that the function of betaPix-bL is more heavily required during the early stages of brain development.
authors.affiliation: School of Biological Sciences, Seoul National University, Seoul 151-742, South Korea.
authors.forename: Sangmyung
authors.initials: S
authors.lastname: Rhee
authors.forename: Soo Jung
authors.initials: SJ
authors.lastname: Yang
authors.forename: Seung Joon
authors.initials: SJ
authors.lastname: Lee
authors.forename: Dongeun
authors.initials: D
authors.lastname: Park
mesh_terms: D020121:5' Untranslated Regions / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000378:metabolism; D019556:COS Cells; D018797:Cell Cycle Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics*; D002522:Chlorocebus aethiops; D018387:Codon, Initiator / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D020662:Guanine Nucleotide Exchange Factors / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis / Q000235:genetics*; D020033:Protein Isoforms / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D064067:Rho Guanine Nucleotide Exchange Factors; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism; D014162:Transfection
chemical_list: D020121:5' Untranslated Regions; D018797:Cell Cycle Proteins; D018387:Codon, Initiator; D018076:DNA, Complementary; D020662:Guanine Nucleotide Exchange Factors; D020033:Protein Isoforms; D012333:RNA, Messenger; D011994:Recombinant Proteins; D064067:Rho Guanine Nucleotide Exchange Factors