Department of Molecular Biology
University of Texas Southwestern Medical Center
The clan CE enzymes include families of enzymes with members from plants, animals, bacterial pathogens and viruses. The Ulp1 family of enzymes includes a desumolylating enzyme, XopD, a type III secreted effector from Xanthomonas campestris pv. vesicatoria, with strict specificity for its plant SUMO substrates. By solving the XopD crystal structure and incorporating the structural information with sequence alignments and enzyme assays, we were able to elucidate determinants of the rigid SUMO specificity exhibited by the Xanthomonas virulence factor XopD. Another family of enzymes, the YopJ family, which has members in both plant and animal pathogens, was initially thought to share similar activities based on structural predictions. Instead what we have found is that this family encodes an acetyl transferase activity, which is mechanistically similar to the predicted peptidase activity. A more in depth view on the evolution of this clan of enzymes from plant and animal pathogens will be discussed. Production of type I interferons (IFNs) by mammalian cells serves as a first line of defense against invasion by viruses and some bacteria. The signaling events that trigger the transcription of type I IFNs involve the coordinate activation of several transcription factors, including interferon response factors (IRFs). Initiation of type I IFN transcription requires signal dependent phosphorylation. My seminar will focus on the signaling events in the host cell that are elicited by virus infection. In particular, I'll discuss the role of two kinases, TBK1 and IKKε, in coordinating the host response to infection.