Identification of the KRIT1 Protein by LexA-Based Yeast Two-Hybrid System

Cerebral cavernous malformation (CCM) is a vascular malformation of the central nervous system that is associated with leaky capillaries, and a predisposition to serious clinical conditions including intracerebral hemorrhage and seizures. Germline or sporadic mutations in the CCM1/KRIT1 gene are responsible for the majority of cases of CCM. In this article, we describe the original characterization of the CCM1/KRIT1 gene. This cloning was done through the use of a variant of the yeast two-hybrid screen known as the interaction trap, using the RAS-family GTPase KREV1/RAP1A as a bait. The partial clone of KRIT1 (Krev1 Interaction Trapped) initially identified was extended through 5'RACE and computational analysis to obtain a full-length cDNA, then used in a sequential screen to define the integrin-associated ICAP1 protein as a KRIT1 partner protein. We discuss how these interactions are relevant to the current understanding of KRIT1/CCM1 biology, and provide a protocol for library screening with the Interaction Trap.