Alternative titles; symbols
HGNC Approved Gene Symbol: INTS6
Cytogenetic location: 13q14.3 Genomic coordinates (GRCh38): 13:51,334,405-51,453,036 (from NCBI)
INTS6 is a subunit of the Integrator complex, which contains at least 12 subunits. The Integrator complex associates with the C-terminal domain of RNA polymerase II large subunit (POLR2A; 180660) and mediates 3-prime end processing of small nuclear RNAs U1 (RNU1; 180680) and U2 (RNU2; 180690) (Baillat et al., 2005). INTS6 also has a role in stabilizing MCM7 (600592) during the G1/S phase transition (Buchsbaum et al., 2007).
By searching for genes in a region of chromosome 13 that showed loss of heterozygosity in lung carcinomas, followed by screening a fetal brain cDNA library, Wieland et al. (1999) cloned INTS6, which they called DICE1. The deduced 887-amino acid protein has a calculated molecular mass of 100 kD. It has an N-terminal RGD sequence characteristic of integrins (see 135630), a DEAD box characteristic of ATP-dependent helicases, a potential N-glycosylation site, several protein phosphorylation sites, and a nuclear sorting signal. Northern blot analysis detected major 4.4- and minor 6.9-kb DICE1 transcripts in all 8 adult human tissues examined and in all 5 fetal tissues examined. A 4-kb transcript was also detected in adult heart, brain, and skeletal muscle. Zoo blot analysis detected a single DICE1 ortholog in several mammals and in chicken.
Using RT-PCR, Wieland et al. (2001) identified 2 DICE1 splice variants. One variant lacks exon 3 and encodes a protein lacking 50 amino acids at the N-terminal end. This variant was expressed exclusively in adult human brain. The other variant lacks exons 5 through 7 and encodes a protein lacking amino acids 144 to 298. Database analysis revealed orthologs of DICE1 in mouse, rat, fruit fly, and nematode. The DEAD box motif was the most highly conserved region. Fluorescence-tagged DICE1 localized predominantly to the nucleus of transfected COS-7 cells.
By SDS-PAGE of proteins that copurified with INTS11 (CPSF3L; 611354) in HEK293 cells, Baillat et al. (2005) identified INTS6 as a subunit of the Integrator complex. Baillat et al. (2005) stated that the INTS6 protein contains a von Willebrand factor type A domain.
Using a yeast 2-hybrid screen, Buchsbaum et al. (2007) showed that human INT6 interacted with a C-terminal region of MCM7 (600592). Cotransfection, immunoprecipitation analysis, and protein pull-down assays revealed a direct interaction between recombinant and endogenous INT6 and MCM7. Mutation analysis identified a C-terminal region of INT6 and a region outside the MCM box of full-length MCM7 that were required for the interaction. MCM7 associated with chromatin was polyubiquitinated and degraded by the proteasome during S phase, and INT6 interacted with both unmodified and polyubiquitinated MCM7. Overexpression of INT6 stabilized MCM7 against degradation, and knockdown of INT6 via small interfering RNA resulted in early loss of MCM7 during S phase in synchronized human cell lines. INT6 also preferentially interacted with chromatin-bound and soluble MCM7 in the nucleoplasm, but not in the cytoplasm. Depletion of INT6 resulted in signs of replication fork stress. Buchsbaum et al. (2007) concluded that INT6 restrains degradation of MCM7 during DNA replication by protecting its polyubiquitinated form from proteasomal degradation.
Wieland et al. (2001) determined that the INTS6 gene contains 18 coding exons, 2 promoters, and 1 enhancer. The proximal promoter contains a TATA box, and the upstream promoter is TATA-less. The upstream region encompassing both promoters is GC rich.
Using FISH and genomic sequence analysis, Wieland et al. (2001) mapped the INTS6 gene to chromosome 13q14.3.
Baillat, D., Hakimi, M.-A., Naar, A. M., Shilatifard, A., Cooch, N., Shiekhattar, R. Integrator, a multiprotein mediator of small nuclear RNA processing, associates with the C-terminal repeat of RNA polymerase II. Cell 123: 265-276, 2005. [PubMed: 16239144] [Full Text: https://doi.org/10.1016/j.cell.2005.08.019]
Buchsbaum, S., Morris, C., Bochard, V., Jalinot, P. Human INT6 interacts with MCM7 and regulates its stability during S phase of the cell cycle. Oncogene 26: 5132-5144, 2007. [PubMed: 17310990] [Full Text: https://doi.org/10.1038/sj.onc.1210314]
Wieland, I., Arden, K. C., Michels, D., Klein-Hitpass, L., Bohm, M., Viars, C. S., Weidle, U. H. Isolation of DICE1: a gene frequently affected by LOH and downregulated in lung carcinomas. Oncogene 18: 4530-4537, 1999. [PubMed: 10467397] [Full Text: https://doi.org/10.1038/sj.onc.1202806]
Wieland, I., Ropke, A., Stumm, M., Sell, C., Weidle, U. H., Wieacker, P. F. Molecular characterization of the DICE1 (DDX26) tumor suppressor gene in lung carcinoma cells. Oncol. Res. 12: 491-500, 2001. [PubMed: 11939413] [Full Text: https://doi.org/10.3727/096504001108747503]