DOMAIN-PHOS: Towards large-scale functional characterization of protein phosphorylation

Objective

In recent decades, phosphoproteomics has greatly advanced our ability to quantify protein phosphorylation. However, characterizing the functional consequences of these phosphorylation events remains challenging, with only ~6% of recorded events having an associated function. This project aims to bridge this gap by developing a high-throughput method for characterizing biochemical functions of phospho-events. The proposed approach, supported by preliminary data, leverages the fact that some protein domains recognize phosphorylation of other proteins, thereby defining the function of both the binder and the phospho-substrate. For example, 37 human proteins contain the phospho-binding Forkhead-Associated (FHA) domain, each with a slightly altered sequence influencing substrate choice. FHA proteins act in various processes, including DNA damage response and cytoskeletal movements, areas of expertise for the applicant. The project involves GFP-tagging all human FHA domains for use in affinity pulldowns, followed by mass spectrometry for comparative analysis of phospho-substrates. For validation, we will perform large-scale reciprocal phosphopeptide pulldowns, a technique developed in the host lab. The combination of the applicant's expertise and the host lab's methodology creates a strong synergy. To understand structure-function relations, we will model interactions of shortlisted FHA:phospho-substrate pairs using AlphaFold3. Additionally, we will conduct phenome-wide association studies to find links between mutations in interaction pairs and disease states, including the functional follow-up on disease-relevant findings. The appeal of this approach extends beyond expanding FHA domain biology, as it has the potential to generalize to other post-translational modification- (PTM-) binding domains. This method could start a field describing PTM-associated functions at scale, enabling easier causative linking of protein function, mutation, and disease.