Vaults are large cytoplasmic ribonucleoproteins of about 13 MD. They are composed of a major vault protein, MVP (605088), 2 minor vault proteins, TEP1 (601686) and PARP4 (607519), and a nontranslated RNA component, VTRNA1-1 (Kickhoefer et al., 1999).

By PCR of a human genomic DNA library, Kickhoefer et al. (1998) cloned VTRNA1-1, which they called HVG1. The 96-base RNA contains an internal RNA polymerase III (see 606007)-type promoter element and ends with a typical polymerase III termination signal.

Kickhoefer et al. (2003) found that the mouse genome contains only 1 expressed vault RNA gene, which they called Mvr1. Northern blot analysis detected a single Mvr1 transcript in all mouse tissues examined, with highest expression in lung, heart, and spleen and lowest expression in brain.

Nandy et al. (2009) described the structure of VTRNA1-1. The 99-nucleotide RNA forms an extended stem-loop structure with asymmetric internal bulges. It contains characteristic internal polymerase III A-box and B-box promoter elements and a downstream B2-box motif. Size exclusion chromatography of fractionated HeLa cells, followed by Northern and Western blot analyses, detected about 5% of the VTRNA1-1 and VTRNA1-2 content eluting with MVP, while 95% remained in the supernatant.

Kickhoefer et al. (1998) found that HVG1, but not HVG2 (VTRNA1-2; 612696) or HVG3 (VTRNA1-3; 612696), associated with vaults in human cell lines. However, only a proportion of HVG1 associated with vaults, and HVG1 not associated with vaults remained in the soluble fraction. Expression of MVP and HVG1 and assembly of vaults increased up to 15-fold in several drug-resistant cell lines compared with the parental cell lines. Increased vault assembly was associated with a concomitant shift of HVG1 from the soluble to the pellet fraction. Kickhoefer et al. (1998) hypothesized that the absolute vault level in cell lines may dictate the extent of drug resistance.

Using Northern blot analysis, Kickhoefer et al. (1999) found that the vault RNAs HVG1 and HVG4 copurified with vaults from all human cell types examined and interacted with mouse Tep1 in a yeast 3-hybrid screen. However, Kickhoefer et al. (2003) reported that HVG4 is not expressed.

Nandy et al. (2009) found that expression of VTRNA1-1, VTRNA1-2, VTRNA1-3, and CBL3 (VTRNA2-1; 614938) was upregulated in cord blood lymphocytes infected with Epstein-Barr virus (EBV). Upregulation was highest for VTRNA1-1 (about 1,100-fold) and lowest for CBL3 (about 3-fold). Expression of VTRNA1-1, VTRNA1-2, and CBL3 was also upregulated by the EBV-related Kaposi sarcoma virus, but not by members of other virus families.

Kickhoefer et al. (2003) determined that the upstream region of the VTRNA1-1 gene contains a TATA-like element, a consensus proximal sequence, and a cAMP response element.

Kickhoefer et al. (2003) stated that the VTRNA1-1, VTRNA1-2, and VTRNA1-3 genes map to a 16-kb region of chromosome 5. A vault RNA pseudogene, HVG4, maps to chromosome X. The only expressed mouse vault RNA gene, Mvr1, maps to chromosome 18.

Nandy et al. (2009) stated that the VTRNA1-1 gene is located near the PCDHA gene cluster (604966), which Wu and Maniatis (1999) mapped to chromosome 5q31.