Michael Summers Seminars - June 1, 2005

Tue May 31 11:26:10 EDT 2005

MIT Postdocs, the following talks being given tomorrow may be of interest.

"Structural Studies of Retroviral Genome Packaging"

Dr. Michael F. Summers
Howard Hughes Medical Institute Investigator
and Professor of Chemistry and Biochemistry
University of Maryland Baltimore County
Wednesday, June 1, 2005
68-181
11:00-12:00 p.m.

Abstract
All retroviruses encapsidate two copies of their 
full-length genomes as they assemble in infected 
cells.  Two RNA molecules are required for strand 
transfer-mediated recombination during reverse 
transcription, which allows viruses to overcome 
otherwise deleterious strand breaks and to 
rapidly respond to evolutionary pressure. Genomic 
RNA exists in virions as dimers, and the overlap 
of RNA elements that promote dimerization and 
encapsidation suggests that these processes may 
be coupled. Both processes are mediated by the 
nucleocapsid domain (NC) of the retroviral Gag 
polyprotein. We have discovered that 
dimerization-induced register shifts in base 
pairing within the _-RNA packaging signal of 
Moloney Murine Leukemia Virus (MLV) expose 
conserved UCUG elements that bind NC with high 
affinity (Kd = 75 ± 12 nM). These elements are 
base-paired and do not bind NC in the monomeric 
RNA. The structure of the NC complex with a 
101-nucleotide "core encapsidation" segment of 
the MLV _-site reveals a network of interactions 
that promote sequence- and structure-specific 
binding by NC's single CCHC zinc knuckle.  The 
structure was determined using a novel approach 
that involved analysis of 3D and 4D 13C-edited 
NMR data obtained for nucleotide-specific, 
isotopically-labeled samples.  Our findings 
support a structural RNA switch mechanism for 
genome encapsidation, in which protein binding 
sites are sequestered by base pairing in the 
monomeric RNA  and become exposed upon 
dimerization to promote packaging of a diploid 
genome.

"Beating the Odds: Increasing
Diversity in the Biomedical Sciences"

Dr. Michael F. Summers
Howard Hughes Medical Institute Investigator
and Professor of Chemistry and Biochemistry,
University of Maryland Baltimore County
Wednesday, June 1, 2005
68-181
3:00-4:00 p.m.
Refreshments outside 68-181 at 2:45 p.m.

Abstract
Although African American students represent 
approximately 11 percent of all students enrolled 
in the nation's colleges and universities, they 
earn not quite seven percent (6.9) of all 
bachelor's degrees and less than two percent 
(1.8) of the doctoral degrees in science and 
engineering.   Colleges and universities, as well 
as national agencies, companies, and foundations, 
regularly send representatives to visit the 
University of Maryland, Baltimore County (UMBC), 
a predominantly white institution emphasizing 
science education and research, because of the 
success over the past decade of our Meyerhoff 
Scholars Program for high-achieving African 
American students in science.  Our experience is 
especially noteworthy given the nation's growing 
diversity and the implications of this 
development for America's future scientific 
workforce.
Since creating the program in 1988, our goal has 
been to build a cadre of well prepared minority 
students who would become leading researchers. 
We have focused on creating a climate that 
attracts serious students, sets high expectations 
of them, and then takes a proactive approach in 
helping them to succeed.  Most important, our 
senior faculty have taken ownership of the 
program and of the student's education, and the 
students, themselves, comprise a community of 
young scholars who support each other and focus 
on the excitement of research. 
	One of the program's distinguishing 
features is its assumption that every student 
competitively selected has the ability not only 
to graduate - given appropriate opportunities and 
resources - but also to excel, because the 
program engenders an expectation of excellence. 
Its components include (1) recruiting top 
minority students in science; (2) a summer bridge 
program; (3) comprehensive merit scholarship 
support; (4) active faculty involvement in 
recruiting, teaching, and students' research 
experiences; (5) strong programmatic values 
including high achievement, study groups, 
tutoring, and preparing for graduate or 
professional school; (6) substantive research 
experiences for students; (7) intensive academic 
advising and personal counseling; (8) active 
involvement of the entire campus; (9) linking 
students with mentors; (10) a strong sense of 
community among the students; (11) communication 
with the students' families; and (12) continuous 
evaluation and documentation of program outcomes.
	This multilevel approach has proven to be 
highly effective.  In fact, Science recently 
listed the Meyerhoff Program among the best 
academic programs of its kind in the nation. 
Approximately 750 undergraduates (including 230 
current students) have enrolled since the program 
began, and approximately 520 students have earned 
STEM degrees, with 85 percent going on to 
graduate and professional programs at 
universities nationwide.  According to recent 
data, UMBC ranked first nationally in the number 
of undergraduate biochemistry degrees awarded to 
African Americans, producing nearly one-third of 
the national total several years ago.   Our 
success at the undergraduate level has led to 
similarly successful initiatives in our graduate 
programs.
Hosts:  Robert Sauer and Graham Walker
Contact:  Brenda Pepe, 3-6077, pepebe at mit.edu

-- 
jfischer at mit.edu    *~*   Ph:     617-253-0386   *~*   Fax:    617-252-1003
M.I.T. Office of the Provost
Room 11-268,  77 Massachusetts Avenue
Cambridge, MA  02139
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