Frequent occurrence of protein isoforms with or without a single amino acid residue by subtle alternative splicing: the case of Gln in DRPLA affects subcellular localization of the products.
Protein isoforms with or without a single amino acid residue make a subtle difference. It has been documented on a few genes that alternative splicing generated such isoforms; however, the fact has attracted little attention. We became aware of a subtle sequence difference in DRPLA, a polyglutamine disease gene for dentatorubral pallidoluysian atrophy. Some reported cDNA sequences lacked 3 nucleotides (nt) (CAG), which were positioned apart from the expandable and polymorphic CAG repeats and also coded for glutamine. We experimentally confirmed that the difference was indeed generated by alternative splicing utilizing two acceptors separated by 3 nt. In DRPLA, the expression ratio of two mRNA isoforms was almost constant among tissues, with the CAG-included form being major. The glutamine-included protein isoform was more predominantly localized in the nucleus. Database searching revealed that alternative splice acceptors, as well as donors, are frequently situated very close to each other. We experimentally confirmed two mRNA isoforms of 3 nt difference in more than 200 cases by RT-PCR and found interesting features associated with this phenomena. Inclusion of 3 nt tends to result in single amino acid inclusion despite the phase of translational frame. The expression ratio sometimes varied extensively among tissues.
Tadokoro
Keiko
K
National Research Institute for Child Health and Development, 2-10-1 Ohkura, Setagaya-ku, Tokyo, 157-8535, Japan.
Yamazaki-Inoue
Mayu
M
National Research Institute for Child Health and Development, 2-10-1 Ohkura, Setagaya-ku, Tokyo, 157-8535, Japan.
Tachibana
Maki
M
National Research Institute for Child Health and Development, 2-10-1 Ohkura, Setagaya-ku, Tokyo, 157-8535, Japan.|Department of Pediatrics, Tokyo Medical University, Tokyo, Japan.
Fujishiro
Mina
M
National Research Institute for Child Health and Development, 2-10-1 Ohkura, Setagaya-ku, Tokyo, 157-8535, Japan.|Laboratory of Nucleic Acid Science, Nihon University, Fujisawa, Japan.
Nagao
Kazuaki
K
National Research Institute for Child Health and Development, 2-10-1 Ohkura, Setagaya-ku, Tokyo, 157-8535, Japan.
Toyoda
Masashi
M
National Research Institute for Child Health and Development, 2-10-1 Ohkura, Setagaya-ku, Tokyo, 157-8535, Japan.
Ozaki
Miwako
M
Laboratory for Memory and Learning, Brain Science Institute, Riken, Wako, Japan.
Ono
Masami
M
Institute of Clinical Endocrinology, Tokyo Women's Medical University, Tokyo, Japan.
Miki
Nobuhiro
N
Institute of Clinical Endocrinology, Tokyo Women's Medical University, Tokyo, Japan.
Miyashita
Toshiyuki
T
National Research Institute for Child Health and Development, 2-10-1 Ohkura, Setagaya-ku, Tokyo, 157-8535, Japan.
Yamada
Masao
M
National Research Institute for Child Health and Development, 2-10-1 Ohkura, Setagaya-ku, Tokyo, 157-8535, Japan. myamada@nch.go.jp.
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D002467:Cell Nucleus / Q000378:metabolism*; D005973:Glutamine / Q000737:chemistry*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D009419:Nerve Tissue Proteins / Q000737:chemistry*; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction
D009419:Nerve Tissue Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; C095278:atrophin-1; D005973:Glutamine; D049452:Green Fluorescent Proteins