Brm transactivates the telomerase reverse transcriptase (TERT) gene and modulates the splicing patterns of its transcripts in concert with p54(nrb).
We report that a DBHS (Drosophila behaviour, human splicing) family protein, p54(nrb), binds both BRG1 (Brahma-related gene 1) and Brm (Brahma), catalytic subunits of the SWI/SNF (switch/sucrose non-fermentable) chromatin remodelling complex, and also another core subunit of this complex, BAF60a. The N-terminal region of p54(nrb) is sufficient to pull-down other core subunits of the SWI/SNF complex, suggesting that p54(nrb) binds SWI/SNF-like complexes. PSF (polypyrimidine tract-binding protein-associated splicing factor), another DBHS family protein known to directly bind p54(nrb), was also found to associate with the SWI/SNF-like complex. When sh (short hairpin) RNAs targeting Brm were retrovirally expressed in a BRG1-deficient human cell line (NCI-H1299), the resulting clones showed down-regulation of the TERT (telomerase reverse transcriptase) gene and an enhancement of ratios of exon-7-and-8-excluded TERT mRNA that encodes a beta-site-deleted inactive protein. All of these clones display growth arrest within 2 months of the Brm-knockdown. In NCI-H1299 cells, Brm, p54(nrb), PSF and RNA polymerase II phosphorylated on CTD (C-terminal domain) Ser(2) specifically co-localize at a region incorporating an alternative splicing acceptor site of TERT exon 7. These findings suggest that, at the TERT gene locus in human tumour cells containing a functional SWI/SNF complex, Brm, and possibly BRG1, in concert with p54(nrb), would initiate efficient transcription and could be involved in the subsequent splicing of TERT transcripts by accelerating exon-inclusion, which partly contributes to the maintenance of active telomerase.
Division of Host-Parasite Interaction, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
Taiji
T
Ito
Hirotaka
H
Watanabe
Nobutake
N
Yamamichi
Shunsuke
S
Kondo
Toshio
T
Tando
Takeshi
T
Haraguchi
Taketoshi
T
Mizutani
Kouhei
K
Sakurai
Shuji
S
Fujita
Tomonori
T
Izumi
Toshiaki
T
Isobe
Hideo
H
Iba
D045744:Cell Line, Tumor; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism; D004265:DNA Helicases / Q000378:metabolism / Q000502:physiology*; D004268:DNA-Binding Proteins; D006801:Humans; D034521:Nuclear Matrix-Associated Proteins / Q000502:physiology*; D009687:Nuclear Proteins / Q000378:metabolism / Q000502:physiology*; D050810:Octamer Transcription Factors / Q000502:physiology*; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics; D016601:RNA-Binding Proteins / Q000502:physiology*; D019098:Telomerase / Q000235:genetics*; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; C083214:NONO protein, human; D034521:Nuclear Matrix-Associated Proteins; D009687:Nuclear Proteins; D050810:Octamer Transcription Factors; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C084011:SMARCA2 protein, human; D014157:Transcription Factors; C509186:TERT protein, human; D019098:Telomerase; C084108:SMARCA4 protein, human; D004265:DNA Helicases