Mammalian mRNA Degradation and Their Roles in

Human Cancers and Other Human Diseases

Our lab is interested in post-transcriptional regulation of mammalian gene expression, in particular the role of mRNA degradation in determining the longevity of cytoplasmic mRNA.  Our research focuses on understanding the mechanism and biological significance of endonucleolytic cleavage in the control of mammalian mRNA degradation.  We are interested in studying mRNAs for genes which are implicated in cancer.  For instance, we have been focusing on identifying novel mammalian endoribonucleases that are capable of cleaving a specific coding region of c-myc mRNA.  c-Myc is a proto-oncoprotein and a transcription factor.  Its mRNA and/or protein are over-expressed in various types of human cancers.  Understanding how to destroy c-myc mRNA may therefore lead to development of new approaches to treat many types of human cancers.

Using traditional biochemical purification, we have identified two novel endoribonucleases that have the ability to cleave c-myc mRNA in vitro.  These proteins have not been previously described to possess endoribonuclease activity.  Our ongoing efforts focus on addressing: (1) Do these endoribonucleases cleave c-myc mRNA and influence its transcript levels in cells?, (2) Do these endoribonucleases cleave other mRNAs, miRNAs or ncRNAs and influence cellular phenotypes?, (3) What are the key RNA structural features and sequences that are recognized and cleaved by these enzymes?, and (4) Do these enzymes possess common or unique endoribonuclease domain?

Our lab is also studying an RNA-binding protein called Coding Region Determinant-Binding Protein or CRD-BP.  We have recently shown that CRD-BP binds avidly to a coding region of c-myc mRNA in vitro to protect the c-myc mRNA from endonucleolytic cleavage by the recently identified endonuclease.  Currently, we are addressing the following questions: (1) Can CRD-BP protects c-myc mRNA from endonucleolytic cleavage by the endoribonucleases in cells?, (2) What small molecules are capable of breaking CRD-BP-c-myc mRNA interaction?, and (3) Can the small molecules that break CRD-BP-c-myc mRNA interaction influence c-myc mRNA abundance in cancer cells?

We have recently established a fluorescence-based assay to measure endoribonuclease activity.  We are currently using this assay to rapidly: (1) characterize the biochemical properties of identified endoribonucleases, and (2) identify further novel mammalian endoribonucleases.