Alternative titles; symbols
HGNC Approved Gene Symbol: DIRAS3
Cytogenetic location: 1p31.3 Genomic coordinates (GRCh38) : 1:68,045,962-68,050,627 (from NCBI)
The Ras (see HRAS; 190020) superfamily of protooncogenes is among the most commonly activated in a number of cancers, including breast and ovarian tumors. By differential display PCR and by screening a normal ovarian epithelial cell cDNA library, Yu et al. (1999) identified a cDNA encoding ARHI, which they termed NOEY2. Sequence analysis predicted that the 229-amino acid ARHI protein shares 54% amino acid homology with HRAS and 56 to 62% homology with RAS-related proteins (e.g., RAP1A; 179520). ARHI contains a highly conserved GTP-binding domain, a putative effector domain distinct from that of RAS and RAP proteins, and a C-terminal membrane localization motif. Northern blot analysis detected a 1.9-kb ARHI transcript in all normal breast and ovarian epithelial cell cultures tested, as well as in normal ovary, heart, liver, pancreas, and brain. Expression was absent in nearly all breast and ovarian cancer cell lines and all primary ovarian cancer cell lines tested. Western blot analysis detected a 26-kD ARHI protein in all normal breast and ovarian cell lines, but not in any breast and ovarian cancer cell lines tested.
Using RT-PCR of 19 human tissues, Niemczyk et al. (2013) found very high DIRAS3 expression in ovary and pancreas, with much lower expression in most other tissues. Little to no expression was present in adipose and placenta.
Yu et al. (1999) determined that the ARHI gene has 2 exons.
Niemczyk et al. (2013) showed that the DIRAS3 gene has differentially methylated regions (DMRs) corresponding to the transcription start site and an upstream CpG island (DMR1 and DMR2, respectively), as well as a third DMR corresponding to a CpG island within exon 2 (DMR3). DMR1 and DMR2 are methylated on the maternal allele only.
By PCR analysis of a genomic library and by FISH, Yu et al. (1999) mapped the DIRAS3 gene to 1p31, a region that is frequently deleted in breast and ovarian cancer due to loss of heterozygosity.
Niemczyk et al. (2013) found that the DIRAS3 gene maps within an intronic region of the GNG12AS1 gene (615406) on the opposite strand.
Yu et al. (1999) found that expression of ARHI in breast and ovarian cancer cell lines, but not in lung cancer cell lines, led to growth inhibition. Stimulation of normal cell lines with growth factors led to decreased expression of ARHI as well as the cell growth inhibition-associated protein WAF1 (CDKN1A; 116899). RFLP analysis of genomic DNA of informative families showed that ARHI is expressed monoallelically and is imprinted maternally.
Fujii et al. (2003) found that treatment with CpG demethylating agents and/or histone deacetylase inhibitors could reactivate both the silenced and the imprinted alleles of ARHI. Reactivation of ARHI expression by these reagents was related to the methylation status of the CpG islands in the ARHI promoter, especially CpG island II. Chromatin immunoprecipitation assays revealed that histone H3 (see 602810) lysine-9/18 acetylation levels associated with ARHI in normal cells were significantly higher than those in breast cancer cell lines that lacked ARHI expression. Treatment with a CpG demethylating agent and/or histone deacetylase inhibitor increased ARHI expression in breast cancer cells, with a corresponding increase in histone H3 lysine-9/18 acetylation and decrease in histone H3 lysine-9 methylation.
Weber et al. (2005) studied the frequency and mechanism of ARHI silencing in benign and malignant thyroid neoplasia. They demonstrated that underexpression of ARHI occurs principally in follicular thyroid carcinoma (FTC; see 188470) (P = 0.0018), including its oncocytic variant (11 of 13), even at minimally invasive stage, but not classic papillary thyroid carcinoma (PTC; see 188550) (2 of 7) or follicular adenoma (FA) (3 of 14). FTCs showed strong allelic imbalance with reduction in copy number/loss of heterozygosity (LOH) in 69%, compared with less than 10% for FAs. In combination with LOH data, bisulfite sequencing in a subset of samples revealed a symmetric methylation pattern for FA, likely representing 1 unmethylated allele and 1 presumptively imprinted allele, whereas FTC showed a virtually complete methylation pattern, representing LOH of the nonimprinted allele with only the hypermethylated allele remaining. Weber et al. (2005) showed that pharmacologic inhibition of histone deacetylation, but not demethylation, could reactivate ARHI expression in the FTC133 FTC cell line. Weber et al. (2005) concluded that silencing of the putative maternally imprinted tumor suppressor gene ARHI, primarily by large genomic deletion in conjunction with hypermethylation of the genomically imprinted allele, serves as a key early event in follicular thyroid carcinogenesis.
To study the biologic function of the ARHI tumor suppressor gene, Xu et al. (2000) generated ARHI transgenic mice with ARHI expression driven by the cytomegalovirus promoter. Overexpression of ARHI in transgenic mice resulted in a decrease in body size and impaired development in multiple organs. Defects were particularly evident in fertility and postpartum lactation. The data suggested that ARHI is a negative regulator of murine growth as well as of the development and function of the breast and ovary.
Fujii, S., Luo, R. Z., Yuan, J., Kadota, M., Oshimura, M., Dent, S. R., Kondo, Y., Issa, J.-P. J., Bast, R. C., Jr., Yu, Y. Reactivation of the silenced and imprinted alleles of ARHI is associated with increased histone H3 acetylation and decreased histone H3 lysine 9 methylation. Hum. Molec. Genet. 12: 1791-1800, 2003. [PubMed: 12874100] [Full Text: https://doi.org/10.1093/hmg/ddg204]
Niemczyk, M., Ito, Y., Huddleston, J., Git, A., Abu-Amero, S., Caldas, C., Moore, G. E., Stojic, L., Murrell, A. Imprinted chromatin around DIRAS3 regulates alternative splicing of GNG12-AS1, a long noncoding RNA. Am. J. Hum. Genet. 93: 224-235, 2013. [PubMed: 23871723] [Full Text: https://doi.org/10.1016/j.ajhg.2013.06.010]
Weber, F., Aldred, M. A., Morrison, C. D., Plass, C., Frilling, A., Broelsch, C. E., Waite, K. A., Eng, C. Silencing of the maternally imprinted tumor suppressor ARHI contributes to follicular thyroid carcinogenesis. J. Clin. Endocr. Metab. 90: 1149-1155, 2005. [PubMed: 15546898] [Full Text: https://doi.org/10.1210/jc.2004-1447]
Xu, F., Xia, W., Luo, R. Z., Peng, H., Zhao, S., Dai, J., Long, Y., Zou, L., Le, W., Liu, J., Parlow, A. F., Hung, M.-C., Bast, R. C., Jr., Yu, Y. The human ARHI tumor suppressor gene inhibits lactation and growth in transgenic mice. Cancer Res. 60: 4913-4920, 2000. [PubMed: 10987306]
Yu, Y., Xu, F., Peng, H., Fang, X., Zhao, S., Li, Y., Cuevas, B., Kuo, W.-L., Gray, J. W., Siciliano, M., Mills, G. B., Bast, R. C., Jr. NOEY2 (ARHI), an imprinted putative tumor suppressor gene in ovarian and breast carcinomas. Proc. Nat. Acad. Sci. 96: 214-219, 1999. [PubMed: 9874798] [Full Text: https://doi.org/10.1073/pnas.96.1.214]