bio

I have recently completed my Ph.D. in Microbiology and Molecular Genetics at Emory University in Atlanta, GA under the direction of Dr. Gordon G. Churchward. My doctoral research focused on conjugation of the broad host-range, conjugative transposon Tn916. Tn916 is an 18kb conjugative transposon originally discovered in Enterococcus faecalis DS16. We were interested in understanding the mechanism by which this element conjugates as it originated in a Gram-positive organism (where less is known about conjugation mechanisms) and has a very broad host range (transferring to both Gram-positive and Gram-negative organisms). Our focus was on initiation of conjugation. Conjugal transfer of elements like Tn916 requires an origin of transfer (oriT) and a relaxase enzyme that initiates transfer by cleaving oriT. Two proteins, Orf20 and Orf23, were identified as possible relaxases by BLASTP analysis. Orf20 was subsequently shown to act as the Tn916 relaxase with the integrase, Int, acting as a specificity factor, an unprecedented role for a recombinase. Orf23 was shown to be a nonspecific DNA-binding protein; however, interactions with different DNAs suggest there may be a sequence component to its ability to bind DNA. This protein may interact with DNA to change its secondary structure and may be involved in properly adjusting the DNA topology at oriT. The uniqueness of the proteins involved in conjugation of Tn916 has lead to a proposed name change from tra to tec (transposon-encoded conjugation proteins).