Project Summary/Abstract A context dependent role of autophagy has been implicated in cancer, and modulation of autophagy has becoming a new experimental strategy in cancer treatment. Sequestosome1 (SQSTM1/p62) is a known autophagy adaptor and mediates cell proliferation, survival and death through multiple signaling pathways, including mTORC1 activation and autophagy. Accumulation and misregulation of p62 has been linked to tumor formation, progression and resistance to therapy, thus p62 is emerging as a new therapeutic target in cancer treatment. Recent studies from our lab and others revealed a critical role of p62 in the autophagic cascade responsible for sequestration of misfolded proteins generated during endoplasmic reticulum (ER) stress, and importantly, small molecules targeting the ZZ domain of p62 (p62ZZ) have been shown to inhibit multiple myeloma (MM) cell growth. Yet how p62ZZ ligands inhibits MM cell growth and more broadly, how p62 senses stress and regulates cellular pathways are still not fully understood. We also found that p62ZZ binds histone H3 tail, linking the chromatin targeting of p62 to a recently discovered role of p62 in DNA damage response, which is frequently targeted in cancer therapeutics. MM is still an uncurbable blood cancer today and is characterized by constitutive high ER-stress. We hypothesize that the conformational state and intracellular level of p62, controlled by its interaction with cellular signals, is the determinant to activate a specific pathway such as mTORC1 activation, autophagy and DNA repair. Treating cells with p62 ligands hijacks p62 and inhibits its normal function, leading to accumulation of stress and cell growth suppression. This application aims to determine the mechanism of action that directly targeting p62ZZ inhibits MM cell growth (Aim1);; elucidate the molecular mechanisms underlying p62-dependent selective activation of mTORC1 or autophagy pathways (Aim2);; and define the role of p62 chromatin targeting in DNA damage response (Aim3). The K99 phase of the proposed studies will be conducted under the mentorship of Dr. Tatiana Kutateladze, who is a well-regarded structural biologist in the epigenetics field and has a strong record in mentoring young scientists. For the cellular experiments related to autophagy and DNA damage response, I will learn from and collaborate with Dr. Andrew Thorburn, a leading expert in the field of autophagy, and Dr. Joshua Black who is an expert in chromatin biology. My progress in research and career development will be closely monitored by the dedicative and supportive advisory committee. The goal for the K99 phase is to complete Aim1 and initiate the rest aims of the proposal and build a strong foundation for my tra...