Parafibromin, a transcription factor associated with the PAF complex, is encoded by the HRPT2 gene, mutations of which cause the hyperparathyroidism-jaw tumor syndrome (OMIM145001). To elucidate the function of parafibromin, we generated conventional and conditional Hrpt2 knockout mice and found that Hrpt2 ؊/؊ mice were embryonic lethal by embryonic day 6.5 (E6.5). Controlled deletion of Hrpt2 after E8.5 resulted in apoptosis and growth retardation. Deletion of Hrpt2 in adult mice led to severe cachexia and death within 20 days. To explore the mechanism underlying the embryonic lethality and death of adult mice, mouse embryonic fibroblasts (MEFs) were cultured and Hrpt2 was deleted in vitro. Hrpt2 ؊/؊ MEFs underwent apoptosis, while Hrpt2 ؉/؉ and Hrpt2 ؉/؊ MEFs grew normally. To study the mechanism of this apoptosis, Hrpt2 ؉/؉ and Hrpt2 ؊/؊ MEFs were used in cDNA microarray, semiquantitative reverse transcription-PCR, and chromatin immunoprecipitation assays to identify genes regulated by parafibromin. These revealed that Hrpt2 expression and the parafibromin/PAF complex directly regulate genes involved in cell growth and survival, including H19, Igf1, Igf2, Igfbp4, Hmga1, Hmga2, and Hmgcs2. Thus, our results show that expression of Hrpt2 and parafibromin is pivotal in mammalian development and survival in adults and that these functions are likely mediated by the transcriptional regulation of growth factors.Loss-of-function HRPT2 mutations are associated with the autosomal dominantly inherited hyperparathyroidism-jaw tumor (HPT-JT) syndrome. Patients with HPT-JT develop parathyroid tumors, ossifying fibromas of the mandible and maxilla, uterine tumors, and renal abnormalities that may include cysts, mixed epithelial and stromal tumors, and Wilms' tumors (3). The HRPT2 gene is located on chromosome 1q31.2, and the observed loss of heterozygosity in HPT-JT-associated tumors and the identification of combined somatic and germ line HRPT2 mutations in some other HPT-JT tumors indicate that HRPT2 is a tumor suppressor gene (2, 7). In addition, HRPT2 mutations are frequently found in sporadic parathyroid carcinomas (18, 43), and expression of parafibromin, which is the 531-amino-acid protein encoded by HRPT2 (7), in parathyroid carcinomas has been reported to be lower than in normal parathyroid tissues (49). Sporadic human renal tumors, from two patients, have also been reported to have frequent allelic imbalances and to harbor HRPT2 mutations (55). These findings are consistent with a tumor suppressor role for HRPT2 and its encoded protein, parafibromin.Parafibromin shares 32% sequence similarity with the Saccharomyces cerevisiae protein Cdc73, which is a component of the yeast polymerase II-associated factor (PAF) complex, and it also has homologs in Caenorhabditis elegans, Drosophila melanogaster, and mice (7). The yeast PAF complex, which is associated with RNA polymerase II and is composed of Paf1, Ctr9, Leo1, Rtf1, and Cdc73, is involved in RNA polymerase II-mediated transcription initiation and elongation (36),...

Oncomir-1 is an oncogenic cluster of microRNAs (miRNA) located on chromosome 13. Previous in vitro studies showed that it is transcriptionally regulated by the transcription factor E2F3. In this report, we combine expression profiling of both mRNA and miRNAs in Wilms' tumor (WT) samples to provide the first evidence that the E2F3-Oncomir-1 axis, previously identified in cell culture, is deregulated in primary human tumors. Analysis of RNA expression signatures showed that an E2F3 gene signature was activated in all WT samples analyzed, in contrast to other kidney tumors. This finding was validated by immunohistochemistry on the protein level. Expression of E2F3 was lowest in early-stage tumors and highest in metastatic tissue. Expression profiling of miRNAs in WT showed that expression of each measured member of the Oncomir-1 family was highest in WT relative to other kidney tumor subtypes. Quantitative PCR confirmed that these miRNAs were overexpressed in WT relative to normal kidney tissue. These results suggest that the E2F3-Oncomir-1 axis is activated in WT. Our study also shows the utility of integrated genomics combining gene signature analysis with miRNA expression profiling to identify protein-miRNA interactions that are perturbed in disease states. [Cancer Res 2008;68(11):4034-8]

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Parafibromin, encoded by the gene HRPT2, is a tumor suppressor protein associated with the RNA polymerase II-associated complex, Paf1 complex. HRPT2 mutations were first identified in patients with the multiple endocrine neoplasia syndrome, hyperparathyroidism-jaw tumor (HPT-JT) syndrome, and have also been found in sporadic parathyroid and renal tumors. However, the mechanisms by which parafibromin suppresses tumor formation remain unknown. In this study, we identify a novel role of parafibromin in the regulation of replication-dependent histones. Both in vitro and in vivo analyses reveal a posttranscriptional role of parafibromin in histone mRNA processing. Downregulation of parafibromin through RNA interference or in vivo mutations lead to uncleaved histone mRNA with polyadenylated tails. These results indicate that parafibromin regulates the 3' processing of histone RNA, an essential component of the cell cycle.