Tuesday, May 5th, 12:30pm

CGSB 8th floor seminar room

Danni Wang, Hochwagen lab, NYU Biology

Transcriptional position effects in the ribosomal DNA array

Repetitive DNA arrays are ubiquitous features of eukaryotic genomes that affect basic cell physiology and disease, but their internal architecture remains poorly understood. The most conserved of these arrays is the ribosomal DNA (rDNA), which consists of hundreds of tandem repeats that organize the nucleolus and are essential for ribosome production. Using repeat-specific reporter lines, we found that RNAPII-dependent gene expression is less silenced in the outer than in the inner repeats of the yeast rDNA array. This transcriptional position effect occurs upon nutrient depletion and rapamycin treatment, and coincides with the condensin- and Hmo1-dependent contraction of the nucleolus.

Dr. Wei-Hsian Lin, Kussell lab lab, NYU Biology Complex interplay between physiology and evolution in the emergence of antibiotic resistance

Antibiotics treatment of microbial populations exerts a strong positive selection for resistant individuals. We used a stochastic promoter to steadily generate a low fraction of resistant in E. coli populations, and applied fluctuating tetracycline selection in microfluidic devices. When tetracycline selection is applied in different temporal patterns, we find that short and long treatment periods are more likely to have resistant sweeps. Intermediate treatment periods allow higher growth rate but reduces the resistant sweep. We measured cell elongations and divisions under different treatment patterns in single cell level to study the physiological response of the cells. Overall, we demonstrated that temporal pattern of selective stress is critical for population adaptation and has clinical implications

Pizza for $2/slice will be available. Bring your own drink.