We have discovered that the CACNA1A gene, which encodes the P/Q type voltage gated calcium channel (VGCC) is bicistronic. The CACNA1A mRNA encodes both the a1A subunit and a second protein, a1ACT, a transcription factor, that is translated as a second open reading frame due to a cryptic internal ribosomal entry site (IRES). Simultaneous expression of two proteins in the same cellular mRNA, one of which is a transcription factor, may be a powerful strategy used by calcium channels and other cellular genes to coordinate expression of an ensemble of genes. To understand this new class of IRES and bicistronic genes we will: 1. Determine how the CACNA1A IRES is regulated by RNA-binding proteins and miRNAs; 2. Define the novel properties of bicistronic genes of the VGCC family. 3. Determine whether altered bicistronic gene expression leads to the complex phenotypes of VGCC disorders. This study will help us to understand the biology of bicistronic cellular genes in particular among other VGCCs, the nature of the IRES regulatory mechanisms and proteins they encode, and the possible role in the pathogenesis and treatment of complex human genetic disease.
We have discovered that the CACNA1A gene, which encodes the P/Q type voltage gated calcium channel (VGCC) a1A subunit is actually bicistronic, and also encodes a second protein, a1ACT, a transcription factor translated from a second open reading frame due to a cryptic internal ribosomal entry site (IRES) within the mRNA coding region. In this study we will characterize the RNA binding proteins and regulation of this novel IRES, and determine whether any of the remainder of the VGCC genes are bicistronic and encode second transcription factor proteins. Finally, we will use transgenic mice to genetically separate the relative contributions the VGCC channel proteins and the VGCC transcription factor proteins.
| Pastor, Parviz Daniel Hejazi; Du, Xiaofei; Fazal, Sarah et al. (2018) Targeting the CACNA1A IRES as a Treatment for Spinocerebellar Ataxia Type 6. Cerebellum 17:72-77 |
| Karginov, Timofey A; Pastor, Daniel Parviz Hejazi; Semler, Bert L et al. (2017) Mammalian Polycistronic mRNAs and Disease. Trends Genet 33:129-142 |
| Miyazaki, Yu; Du, Xiaofei; Muramatsu, Shin-Ichi et al. (2016) An miRNA-mediated therapy for SCA6 blocks IRES-driven translation of the CACNA1A second cistron. Sci Transl Med 8:347ra94 |
