PROJECT SUMMARY AND ABSTRACT
RNA surveillance pathways regulate the quality of cellular RNAs and their abundance. In the nucleus, aberrant,
misfolded, or defective RNAs are degraded primarily by the 3¢-5¢ decay machinery that includes the RNA
exosome, a multi-subunit protein complex that catalyzes 3¢ to 5¢ RNA degradation. The nuclear RNA exosome
targeting substrate is mediated by several protein complexes containing the MTR4 helicase. These include the
nuclear exosome targeting (NEXT) complex and the poly(A) exosome targeting (PAXT) connection which lie
upstream of the RNA exosome. The RNA exosome mutants or overexpressed cofactors contribute to
numerous human diseases, including cancer. Although several studies illuminated the human exosome
structure and functions, there are limited studies on how human NEXT and PAXT engage and prepare their
substrates for their delivery to the RNA exosome.
This research will engage biochemical, structural, and functional approaches to characterize the core
PAXT complex (Aim 1) and determine how substrates are recognized as ribonucleoprotein (RNP) complexes
through nuclear cap-binding complex and poly(A) binding protein (Aim 2). I will leverage the use of reagents
and skills developed in Aim 1 and Aim 2 during the K99 phase to investigate microRNA (miRNA) processing
and turnover by PAXT connection (Aim 3). The outcome of this study will provide novel insights into the
molecular mechanism of target RNP recognition by PAXT and their interaction with the RNA exosome in RNA
decay pathways. Moreover, the study will be expanding to miRNA biogenesis. As RNA decay pathways and
miRNA biogenesis play a fundamental role in gene regulation and cancer, this study can impact human health
and the NCI mission to develop scientific knowledge and support all people to live longer and healthier.
This proposal describes a comprehensive training plan to develop my academic career by investigating
how PAXT recognizes its RNP substrates to stimulate downstream RNA decay and primary miRNA
processing. The purpose of this award is to encourage and prepare my independent research program, and I
will use this period to advance my scientific knowledge and professional skills. During the K99 phase, I will
employ biochemical approaches to reconstitute the PAXT connection with its target and combine them with
cryo-electron microscopy under Dr. Christopher D. Lima’s mentoring. That will extend my technical repertoire
and biological knowledge in RNA biology, cancer biology, and structural biology for future research. Also,
Memorial Sloan Kettering Cancer Center will provide institutional support, including laboratory research
resources, an open scientific environment, and career development to achieve my goals.