TY - JOUR T1 - Crystal structure of human PACRG in complex with MEIG1 JF - bioRxiv DO - 10.1101/783373 SP - 783373 AU - Nimra Khan AU - Dylan Pelletier AU - Simon Veyron AU - Nathalie Croteau AU - Muneyoshi Ichikawa AU - Corbin Black AU - Ahmad Abdelzaher Zaki Khalifa AU - Sami Chaaban AU - Igor Kurinov AU - Gary Brouhard AU - Khanh Huy Bui AU - Jean-François Trempe Y1 - 2019/01/01 UR - http://biorxiv.org/content/early/2019/09/27/783373.abstract N2 - In human, the Parkin Co-Regulated Gene (PACRG) shares a bidirectional promoter with Parkin, a gene involved in Parkinson’s disease, mitochondrial quality control and inflammation. The PACRG protein is essential to the formation of the inner junction between doublet microtubules of the axoneme, a structure found in flagella and cilia. PACRG interacts with tubulin as well as the meiosis expressed gene 1 (MEIG1) protein, which is essential for spermiogenesis in mice. However, the 3D structure of human PACRG is unknown. Here, we report the crystal structure of the C-terminal domain of human PACRG in complex with MEIG1 at 2.1 Å resolution. PACRG adopts an α-helical structure with a loop insertion that mediates a conserved network of interactions with MEIG1. Using the cryo-electron tomography structure of the axonemal doublet microtubule from the flagellated protozoan Chlamydomonas reinhardtii, we generate a model of a mammalian microtubule doublet inner junction, which reveals how PACRG interacts with tubulin subunits in both the A- and B-tubules. Furthermore, the model shows that MEIG1 interacts with β-tubulin on the outer surface of the B-tubule, facing towards the central pair of the axoneme. We also model the PACRG-like protein (PACRGL), a homolog of PACRG with potential roles in microtubule remodelling and axonemal inner junction formation. Finally, we explore the evolution of the PACRG and Parkin head-to-head gene structure and analyze the tissue distribution of their transcripts. Our work establishes a framework to assess the function of the PACRG family of proteins and its adaptor proteins in the function of motile and non-motile cilia. ER -