REGULATORS OF EPIDERMAL GENE EXPRESSION

Stanford University, Stanford CA

Investigators

Linked publications & trials

Abstract

REGULATORS OF EPIDERMAL GENE EXPRESSION PROJECT SUMMARY Epidermal homeostasis is critical for skin barrier function and is disrupted in diseases such as psoriasis, atopic dermatitis, and skin cancer. During the current funding cycle, AR045192 identified new essential roles for specific heterogeneous nuclear ribonucleoproteins (HNRNPs) and ubiquitin- like proteins (UBLs) in epidermal homeostasis. These regulators can exert post-transcriptional and post-translational impacts, respectively, however their actions in the skin are poorly understood. This competing renewal will define how these newly uncovered HNRNPs and UBLs mediate opposing effects on epidermal growth and differentiation. For HNRNP RNA-binding proteins (RBPs), AR045192 knocked out all 33 HNRNPs to uncover new roles for HNRNPC and HNRNPU (pro-progenitor) as well as HNRPNH (pro-differentiation) in epidermal gene expression. HNRNPs exert diverse impacts across RNA lifecycles, however, their actions in epidermis are understudied. AR045192 therefore used non-isotopic ligation-based UV crosslinking immunoprecipitation-mass spectrometry to uncover dynamic assemblies of proteins on mRNAs adjacent to HNRNPC that cooperate with HNRNPC in progenitor mRNA surveillance. Aim I will further define the identity, assembly dependencies, and functions of proteins co-assembled on progenitor and differentiation mRNAs with HNRNPU, and HNRNPH to address the emergent model that specific HNRNPs assemble with distinct combinations of other RBPs on discrete sets of target RNAs to control epidermal homeostasis Conjugation to UBLs, including ubiquitin, NEDD8, and SUMO2, can alter a protein’s localization, interactions, stability, and function, however, roles for UBLs in epidermal homeostasis are not fully characterized. AR045192 knocked out 124 genes encoding all human UBLs, and the enzymes that conjugate them to their target proteins to uncover opposing UBL actions in epidermis. The NEDD8 UBL, along with its corresponding NAE1 and UBA3 enzyme subunits, was essential to maintain undifferentiated progenitor gene expression in human and mouse epidermal cells and tissues. In contrast, the SUMO2 UBL, along with its SAE1 and UBA2 enzyme subunits, was required for differentiation. HNRNPU was identified as NEDD8-tagged in undifferentiated keratinocytes and SUMO2-tagged in differentiating cells; disrupting this reciprocal tagging altered HNRNPU-bound target RNAs. Aim II will apply new methods to characterize the opposing actions of NEDD8 and SUMO2 UBLs in epidermal gene regulation. This effort will expand insight into how specific HNRNP and UBL regulators exert their newly identified essential impacts on epidermal gene expression.