<!doctype html public "-//W3C//DTD W3 HTML//EN">
<html><head><style type="text/css"><!--
blockquote, dl, ul, ol, li { padding-top: 0 ; padding-bottom: 0 }
--></style><title>Michael Summers Seminars - June 1,
2005</title></head><body>
<div>MIT Postdocs, the following talks being given tomorrow may be of
interest.</div>
<hr>
<div><br></div>
<div align="center"><font color="#000000"><i><b>"Structural
Studies of Retroviral Genome Packaging"</b></i></font></div>
<div align="center"><font
color="#000000"><i><b><br></b></i></font></div>
<div align="center"><font color="#000000"><b>Dr. Michael F.
Summers</b></font></div>
<div align="center"><font color="#000000"><b>Howard Hughes Medical
Institute Investigator</b></font></div>
<div align="center"><font color="#000000"><b>and Professor of
Chemistry and Biochemistry</b></font></div>
<div align="center"><font color="#000000"><b>University of Maryland
Baltimore County</b></font></div>
<div align="center"><font color="#000000"><b>Wednesday, June 1,
2005</b></font></div>
<div align="center"><font color="#000000"><b>68-181</b></font></div>
<div align="center"><font color="#000000"><b>11:00-12:00
p.m.</b></font></div>
<div><font color="#000000"><b><br></b></font></div>
<div><font color="#000000"><i><b>Abstract</b></i></font></div>
<div><font color="#000000">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.</font></div>
<div align="right"><br></div>
<hr>
<div><br></div>
<div><br></div>
<div align="center"><font color="#000000"><i><b>"Beating the
Odds: Increasing</b></i></font></div>
<div align="center"><font color="#000000"><i><b>Diversity in the
Biomedical Sciences"</b></i></font></div>
<div><font color="#000000"><i><b><br></b></i></font></div>
<div align="center"><font color="#000000"><b>Dr. Michael F.
Summers</b></font></div>
<div align="center"><font color="#000000"><b>Howard Hughes Medical
Institute Investigator</b></font></div>
<div align="center"><font color="#000000"><b>and Professor of
Chemistry and Biochemistry,</b></font></div>
<div align="center"><font color="#000000"><b>University of Maryland
Baltimore County</b></font></div>
<div align="center"><font color="#000000"><b>Wednesday, June 1,
2005</b></font></div>
<div align="center"><font color="#000000"><b>68-181</b></font></div>
<div align="center"><font color="#000000"><b>3:00-4:00
p.m.</b></font></div>
<div align="center"><font color="#000000"><b>Refreshments outside
68-181 at 2:45 p.m.</b></font></div>
<div><font color="#000000"><b><br></b></font></div>
<div><font color="#000000"><i><b>Abstract</b></i></font></div>
<div><font color="#000000">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.</font></div>
<div><font color="#000000">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. </font></div>
<div><font
color="#000000"><x-tab>
</x-tab>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.</font></div>
<div><font
color="#000000"><x-tab>
</x-tab>This multilevel approach has proven to be highly effective.
In fact,<i> Science</i> 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.</font></div>
<div align="right"><font color="#000000"><b>Hosts: Robert Sauer
and Graham Walker</b></font></div>
<div align="right"><font color="#000000"><b>Contact: Brenda
Pepe, 3-6077, pepebe@mit.edu</b></font></div>
<div><br></div>
<div><br></div>
<x-sigsep><pre>--
</pre></x-sigsep>
<div><font face="Century Gothic" size="-1"
color="#000000">jfischer@mit.edu *~*
Ph: 617-253-0386 *~*
Fax: 617-252-1003</font></div>
<div><font face="Century Gothic" size="-1" color="#000000">M.I.T.
Office of the Provost<br>
Room 11-268, 77 Massachusetts Avenue</font></div>
<div><font face="Century Gothic" size="-1" color="#000000">Cambridge,
MA 02139</font></div>
</body>
</html>