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PRE-mRNA-PROCESSING FACTOR 6; PRPF6

PRE-mRNA-PROCESSING FACTOR 6; PRPF6

Alternative titles; symbolsPRECURSOR mRNA-PROCESSING FACTOR 6, S. CEREVISIAE, HOMOLOG OF; PRP6ANDROGEN RECEPTOR N-TERMINAL DOMAIN-TRANSACTIVATING PROTEIN 1; ANT1...

Alternative titles; symbols

  • PRECURSOR mRNA-PROCESSING FACTOR 6, S. CEREVISIAE, HOMOLOG OF; PRP6
  • ANDROGEN RECEPTOR N-TERMINAL DOMAIN-TRANSACTIVATING PROTEIN 1; ANT1
  • TOM
  • SNRNP102
  • CHROMOSOME 20 OPEN READING FRAME 14; C20ORF14

HGNC Approved Gene Symbol: PRPF6

Cytogenetic location: 20q13.33 Genomic coordinates (GRCh38): 20:63,981,131-64,033,099 (from NCBI)

▼ Cloning and Expression

By sequencing peptides from a 100-kD protein purified from HeLa cell nuclei, followed by EST database analysis and RT-PCR of HeLa cell total RNA, Nishikimi et al. (1999) cloned PRPF6. The deduced 941-amino acid protein has a calculated molecular mass of 106.9 kD. It contains 19 tetratricopeptide repeat (TPR) motifs and a leucine zipper motif. Immunofluorescence analysis confirmed nuclear localization of the protein.

Independently, Makarov et al. (2000) and Yuryev et al. (2000) cloned PRPF6. While Makarov et al. (2000) reported the same protein structure for PRPF6 as Nishikimi et al. (1999), Yuryev et al. (2000) predicted that the 941-amino acid protein contains an N-terminal membrane-anchoring region, followed by a highly charged membrane-proximal domain and 22 TPR motifs. Yuryev et al. (2000) referred to PRF6 as TOM due to its similarity to outer mitochondrial membrane import receptors (see 606081) of S. cerevisiae and N. crassa.

Using the ligand-independent activation function-1 (AF-1) domain of androgen receptor (AR; 313700) as bait in a yeast 2-hybrid screen of a human skin fibroblast cDNA library, Zhao et al. (2002) cloned PRPF6, which they designated ANT1. They identified 19 TPR repeats, 2 LxxLL motifs, and a leucine zipper motif in ANT1. Northern blot analysis of human tissues detected ubiquitous expression of a 4.0-kb ANT1 transcript. Fluorescence-tagged ANT1 clustered in nuclear speckles characteristic of splicing factor foci and in a fine reticular distribution throughout the nucleus. AR colocalized with ANT1 in the diffusely distributed areas, but not in the nuclear speckles.

▼ Gene Structure

Tanackovic et al. (2011) noted that the PRPF6 gene contains 21 exons.

▼ Mapping

Hartz (2011) mapped the PRPF6 gene to chromosome 20q13.33 based on an alignment of the PRPF6 sequence (GenBank AB019219) with the genomic sequence (GRCh37).

▼ Gene Function

An essential step in pre-mRNA spliceosome assembly is interaction between the small nuclear ribonucleoprotein particles (snRNPs) U4/U6 (see 180692) and U5 (see 180691) to form the U4/U6.U5 tri-snRNP. Makarov et al. (2000) found that human PRP6 associated tightly with purified 20S U5 snRNPs. Binding studies suggested that PRP6 interacted directly with the 40-kD (SNRNP40; 607797)/116-kD (EFTUD2; 603892)/220-kD (PRPF8; 607300) protein complex in the U5 snRNP. PRP6 also interacted with purified 13S U4/U6 snRNPs. Makarov et al. (2000) suggested that PRP6 may function as a bridging factor between U5 and U4/U6 snRNPs.

Using protein pull-down assays and coimmunoprecipitation experiments, Zhao et al. (2002) showed that human ANT1 interacted in a ligand-independent manner with full-length AR and with the AR AF-1 domain, but not with the ligand-dependent AR AF-2 domain. ANT1 also interacted with glucocorticoid receptor (GCCR; 138040), but not with estrogen receptor (ER; see 133430), in pull-down assays. ANT1 enhanced transactivation activities mediated by AR and GCCR, but not that mediated by ER. ANT1 also exhibited an independent additive effect on the transactivation functions of cyclin E (CCNE1; 123837) and SRC1 (NCOA1; 602691).

By mutation analysis, Fan et al. (2006) identified 4 functional domains in the ANT1 protein: an N-terminal nuclear localization signal (NLS); a receptor-specific transactivation domain, which largely overlaps the NLS; an intranuclear speckle-localization domain; and an AR AF-1 domain-binding domain located between TPR motifs 4 to 7. ANT1 mutants unable to localize to nuclear speckles retained almost full transactivation capacity against AR AF-1.

▼ Molecular Genetics

Tanackovic et al. (2011) screened all 21 exons of the candidate gene PRPF6 in 188 probands from families segregating autosomal dominant retinitis pigmentosa (RP60; 613983) and identified heterozygosity for a missense mutation at a highly conserved residue in 2 brothers (613979.0001). The authors stated that this was the sixth splicing-factor gene involved in autosomal dominant RP.

▼ ALLELIC VARIANTS ( 1 Selected Example):

.0001 RETINITIS PIGMENTOSA 60
PRPF6, ARG729TRP

In 2 affected brothers from a 4-generation family of European descent segregating autosomal dominant retinitis pigmentosa (RP60; 613983), Tanackovic et al. (2011) identified heterozygosity for a 2185C-T transition in exon 16 of the PRPF6 gene, resulting in an arg729-to-trp (R729W) substitution at a highly conserved residue. The mutation was not found in 1,078 ethnically matched control chromosomes. Immortalized lymphoblasts from the affected sibs showed abnormal localization of endogenous PRPF6 within the nucleus, where the accumulation of protein in Cajal bodies indicated possible impairment in tri-snRNP assembly or recycling. Analysis of endogenous transcripts in cells from 2 sibs revealed intron retention of pre-mRNA bearing specific splicing signals, in a pattern identical to that previously observed by the authors in lymphoblasts carrying mutations in other PRPF genes.

Tags: 20q13.33