Dr. Judith G. Levin was formerly Head, Section on Viral Gene Regulation, Program in Genomics of Differentiation (now the Division of Developmental Biology), Eunice Kennedy Shriver National Institute of Child Health and Human Development until her retirement in 2015. She received a B.A. degree in Chemistry from Barnard College, an M.A. degree in Biochemistry from Harvard University, and a Ph.D. degree in Biochemistry from Columbia University. She spent her entire professional career at the NIH, coming initially to work as a postdoctoral fellow in the laboratory of Dr. Marshall Nirenberg, where she performed studies on protein synthesis and the genetic code. Since the 1970s, Dr. Levin has been investigating the molecular mechanisms involved in retrovirus replication. In her early work, she studied murine leukemia virus (MLV) replication and made several novel discoveries: (i) MLV assembly proceeds in the absence of viral genomic RNA, although virions contain the full complement of viral proteins; (ii) MLV-infected cells contain two non-equilibrating pools of full-length viral RNA, one for encapsidation (short-lived) and the other functioning as the mRNA for the Gag precursor (long-lived), which rationalizes the earlier observation regarding virus assembly; and (iii) A series of papers defining the unique mechanism for MLV translational read-through suppression, which is required for synthesis of the Pol proteins: protease; reverse transcriptase; and integrase.
The broad objective of Dr. Levin’s recent research has been to expand knowledge of HIV replication strategies and host defense mechanisms and thereby contribute to development of new treatments for AIDS patients. She has studied the effects of mutations in structural elements of the HIV-1 capsid protein on infectivity, viral core architecture, and reverse transcription. She has also had a long-standing interest and leadership role in research on the HIV-1 nucleocapsid protein (NC) and has made numerous contributions regarding the critical importance of NC function for specific and efficient reverse transcription. Her major reviews on the nucleic acid chaperone activity of NC (i.e., the ability of NC to remodel nucleic acid structures to form the most thermodynamically stable conformations) have profoundly influenced this area of HIV research and continue to be cited widely in contemporary retrovirus literature. Recently, Dr. Levin has undertaken studies of the human APOBEC3 (A3) proteins, a family of seven cellular cytidine deaminases, which function as DNA mutators and restrict HIV-1 and other pathogens. Her laboratory was one of the first to report biochemical studies of highly purified, catalytically active A3G. This work led to the proposal of a “roadblock” effect of A3G on reverse transcription, indicating that HIV-1 restriction can occur by deaminase-independent as well as deaminase-dependent mechanisms. In other studies, Dr. Levin’s group has exploited a multi-disciplinary approach, targeting the molecular properties of A3A, A3H, and A3B (C-terminal catalytic domain) and their relation to biological activity and three-dimensional NMR solution structure.
The figure shows a schematic representation of the structure of the mature HIV-1 virion (courtesy of Dr. Louis E. Henderson, AIDS Vaccine Program, SAIC Frederick, Inc.). Abbreviations for viral proteins: MA, matrix; CA, capsid; NC, nucleocapsid; PR, protease; RT, reverse transcriptase; IN, integrase; SU, surface glycoprotein; TM, transmembrane. HLA I and HLA II, DR refer to host histocompatibility proteins selectively incorporated into the virion. Note the characteristic cone-shaped core.