Welcome to the lean, mean website of the Bloom Lab, where we do exciting things with yeast. Below you can find a representative sample of some of our recent work. For a more comprehensive summary of our work, most of our publications are available for downloading.

• Determining the stucture of pericentric DNA and cohesin in the inner centromere. Pericentric chromatin is organized by cohesin into a cylinder surrounding the interpolar microtubules of the mitotic spindle. We are testing whether centromere flanking DNA is paired intra-molecularly within the inner centromere cruciform, and whether the structure of the inner centromere and the cohesin cylinder is responsive to changes in tension.
  

• The requirements for cohesin cylinder formation and maintenance and identify how cohesin is restricted to pericentric chromatin. We will determine the requirements for cohesin cylinder formation, and test the hypothesis that specific proteins restrict cohesin to the 30-50kb of pericentric chromatin. We propose that the transition between chromosome arm pairing and pericentric chromatin provides the structural basis for tension sensing in the inner centromere.

Images from left to right: Computer generated mitotic spindle viewed end on, an end on view of SMC3-GFP, computer generated mitotic spindle viewed side on, and a side on view of SMC3-GFP. Flourescent microscopy reveals that cohesin (SMC3) forms a hollow cylindrical structure between the kinetochores (images not shown). This data matches the predictions made by our model for the organization of the mitotic spindle - the chromosomes (represented by orange and red coils) and kinetochore microtubules (light green rods) are arranged in a cylinder around a core of interpolar
microtubules (dark green rods).

• Evaluating the proposal that the conserved chromosome segregation unit is the kinetochore and pericentric cruciform. We will count the number of kinetochore proteins at the microtubule interface in distantly related yeasts. This analysis will reveal whether point vs. regional centromeres have structurally conserved features.

• Examining the physical contributions of the DNA to the mitotic spindle. In particular, we are interested in the potential spring-like properties of DNA, and the tension this applies to the spindle. One approach is to look at the recoil of DNA strands after breakage, both in vivo and in vitro. The following movie is an example DNA breakage and recoil in vivo.

LacO tagged with LacI-GFP

• Identifying how the state of tension of pericentric chromatin is transmitted to the kinetochore DNA linkage to regulate microtubule attachment. We will determine the sites within the kinetochore and pericentric chromatin that are tension-sensitive and identify specific linkages that are compliant. We will use single molecule analysis in live yeast to identify the molecular basis of pericentric chromatin and kinetochore extension and contraction upon change in force.