title: Characterization of Bombyx mori mitochondrial transcription factor A, a conserved regulator of mitochondrial DNA.
abstract: In the present study, we initially cloned and characterized a mitochondrial transcription factor A (Tfam) homologue in the silkworm, Bombyx mori. Bombyx mori TFAM (BmTFAM) localized to mitochondria in cultured silkworm and human cells, and co-localized with mtDNA nucleoids in human HeLa cells. In an immunoprecipitation analysis, BmTFAM was found to associate with human mtDNA in mitochondria, indicating its feature as a non-specific DNA-binding protein. In spite of the low identity between BmTFAM and human TFAM (26.5%), the expression of BmTFAM rescued mtDNA copy number reductions and enlarged mtDNA nucleoids in HeLa cells, which were induced by human Tfam knockdown. Thus, BmTFAM compensates for the function of human TFAM in HeLa cells, demonstrating that the mitochondrial function of TFAM is highly conserved between silkworms and humans. BmTfam mRNA was strongly expressed in early embryos. Through double-stranded RNA (dsRNA)-based RNA interference (RNAi) in silkworm embryos, we found that the knockdown of BmTFAM reduced the amount of mtDNA and induced growth retardation at the larval stage. Collectively, these results demonstrate that BmTFAM is a highly conserved mtDNA regulator and may be a good candidate for investigating and modulating mtDNA metabolism in this model organism.
authors.affiliation: Transgenic Silkworm Research Unit, Division of Biotechnology, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, Owashi, Tsukuba 305-8634, Japan. Electronic address: sumikasashima@affrc.go.jp.
authors.forename: Megumi
authors.initials: M
authors.lastname: Sumitani
authors.affiliation: Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa 277-8562, Chiba, Japan.
authors.forename: Mari
authors.initials: M
authors.lastname: Kondo
authors.affiliation: Division of Functional Biochemistry, Department of Biochemistry, Jichi Medical University, Shimotsuke, Tochigi 329-0498, Japan.
authors.forename: Katsumi
authors.initials: K
authors.lastname: Kasashima
authors.affiliation: Division of Functional Biochemistry, Department of Biochemistry, Jichi Medical University, Shimotsuke, Tochigi 329-0498, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Endo
authors.affiliation: Transgenic Silkworm Research Unit, Division of Biotechnology, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, Owashi, Tsukuba 305-8634, Japan.
authors.forename: Kaoru
authors.initials: K
authors.lastname: Nakamura
authors.affiliation: Transgenic Silkworm Research Unit, Division of Biotechnology, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, Owashi, Tsukuba 305-8634, Japan.
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Misawa
authors.affiliation: Insect-Microbe Research Unit, Division of Insect Sciences, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, Owashi, Tsukuba 305-8634, Japan.
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Tanaka
authors.affiliation: Transgenic Silkworm Research Unit, Division of Biotechnology, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, Owashi, Tsukuba 305-8634, Japan; Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa 277-8562, Chiba, Japan. Electronic address: hsezutsu@affrc.go.jp.
authors.forename: Hideki
authors.initials: H
authors.lastname: Sezutsu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D012831:Bombyx / Q000196:embryology / Q000235:genetics*; D002478:Cells, Cultured; D003001:Cloning, Molecular; D004272:DNA, Mitochondrial / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D006367:HeLa Cells; D006801:Humans; D024101:Mitochondrial Proteins / Q000235:genetics* / Q000502:physiology*; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology*
chemical_list: D004272:DNA, Mitochondrial; D004268:DNA-Binding Proteins; D024101:Mitochondrial Proteins; D014157:Transcription Factors; C422562:mitochondrial transcription factor A
keywords: Bombyx mori; Embryonic RNAi; Mitochondria; Nucleoid; TFAM; mtDNA