WD REPEAT-CONTAINING PROTEIN 33; WDR33

Alternative titles; symbols

• WD REPEAT-CONTAINING PROTEIN, 146-KD; WDC146

HGNC Approved Gene Symbol: WDR33

Cytogenetic location: 2q14.3 Genomic coordinates (GRCh38): 2:127,701,026-127,811,186 (from NCBI)

▼ Description

WDR33 is a subunit of cleavage and polyadenylation specificity factor (CPSF), which mediates 3-prime cleavage and AAUAAA-dependent polyadenylation of mRNAs (Schonemann et al., 2014).

▼ Cloning and Expression

Ito et al. (2001) cloned human WDR33, which they called WDC146. The deduced 1,376-amino acid WDC146 has a calculated molecular mass of 146 kD. It contains 8 N-terminal WD40 repeats, a central collagen-like domain, and a C-terminal domain composed mainly of glycine, proline, and arginine (GPR domain). The human WDC146 protein shares about 95% amino acid identity with its rodent orthologs, including mouse and rat. Northern blot analysis of human tissues detected a 4-kb WDC146 transcript preferentially expressed in testis, with weak expression in all other tissues examined except colon and small intestine. A similar expression pattern was found in mouse tissues. In situ hybridization of adult rat testis revealed Wdc146 mRNA in the pachytene stage of spermatocyte division, but not in other stages. Expression was mainly present in spermatocytes and weak in round spermatids, but not detected in elongate spermatids. In rat thymus, Wdc146 expression was observed in cortex, but not in medulla. Wdc146 expression was also detected in white pulp and marginal band of rat spleen, but not in red pulp. Fluorescence-tagged WDC146 protein was expressed at nuclear and perinuclear regions of ITO-II, Saos2, NIH3T3, and 293 cells.

▼ Gene Function

Using in vitro and in vivo assays, Chan et al. (2014) found that human WDR33 contacted AAUAAA directly. Analyses with radiolabelled synthetic RNAs and immunoprecipitation showed that WDR33 specifically bound to a narrow region spanning the AAUAAA hexamer.

Using purified CPSF subunits from an insect cell expression system, Schonemann et al. (2014) reconstituted CPSF with different combinations of subunits in vitro and found that 4 of the 7 CPSF subunits were necessary and sufficient for polyadenylation activity: CPSF160 (CPSF1; 606027), CPSF30 (CPSF4; 603052), FIP1 (RRAGA; 612194), and WDR33. WDR33 was required and appeared to underlie the ability of CPSF to bind substrate RNA and trigger polyadenylation. Transcriptomewide identification of WDR33 targets by photoactivatable ribonucleoside-enhanced cross-linking and immunoprecipitation demonstrated that WDR33 recognized AAUAAA signal in vivo with high specificity and bound to regions containing the AAUAAA sequence. Pull-down analysis further revealed that the N-terminal region of WDR33 containing the WD40 repeats was essential for RNA binding.

▼ Gene Structure

Ito et al. (2001) found that the WDR33 gene contains 22 exons that are dispersed into 3 clusters spanning approximately 105 kb. Exon 1 is noncoding, and the initiation codon is located within exon 2.

▼ Mapping

Ito et al. (2001) reported that the WDR33 had been mapped to chromosome 2q14.2-q21.1 by FISH.

Gross (2018) mapped the WDR33 gene to chromosome 2q14.3 based on an alignment of the WDR33 sequence (GenBank BC013990) with the genomic sequence (GRCh38).