Community Spotlight

Karen Almeida

kalmeida@ric.edu
456-9665
Clarke Science 108

INBRE grant title: Genome Stability through Bloom Syndrome Helicase and Rad51 Complex Formation

Research in my lab focuses on the repair of damaged DNA, specifically damage encountered during active replication or S-phase. DNA is a dynamic biopolymer that contains the genetic information for life. The accurate copying of this information is critical to survival yet the DNA is constantly damaged from the byproducts of metabolism within a cell as well as from exposure to toxins in the environment. The state of persistent DNA damage leads to undesired genetic changes, perhaps even cancer. Therefore, cells have devised numerous pathways for the repair of DNA damage.

There are two pathway models by which a cell can tolerate DNA damage during replication to successfully complete S-phase. Model one describes the stalling of the replication fork prior to encountering the damage site followed by a reversal of the replication fork to expose the damage in a form recognized by DNA repair pathways. This stalling is thought to be facilitated by Bloom Syndrome Helicase (Blm), an enzyme responsible for unwinding DNA in the 3’->5’ direction. Mutation within the Blm protein is responsible for the rare human autosomal recessive disorder known as Bloom Syndrome. Model two depicts the encounter of the replication fork with a single strand break in the parental strand. Such an encounter could result in replication fork collapse, requiring recombinational repair to reinsert the broken end into the genome. Rad51 is the central protein in recombinational repair and could facilitate the restoration of the fork. Interestingly, Blm and Rad51 physically interact with each other although current thinking places them in two distinct pathways.

Undergraduate research in my lab is critical for success. Individual projects include:

• The subcloning of cDNA for the full-length Blm protein as well as specific deletion mutants that will assist in determining the exact residues that contact Rad51
• The over expression and purification of Blm proteins to be used for in vitro biochemical assays
• Determining Protein-DNA binding interactions that will be used to assess the affect of amino acid residue deletions
• Determining Protein-Protein binding interactions again to be used to assess the affect of deletion mutants