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Sbash is a temperate bacteriophage that infects Mycobacterium smegmatis. It was assigned to cluster I2 based on gene-content similarity of 35% or higher to sequenced bacteriophages present in the Actinobacteriophage database, phagesDB. Its genome was annotated in 2014 and found to include 89 protein-coding genes, only 22 of which were assigned functions based on bioinformatic analysis. We are using a genetic screen to identify functions of phage genes for which no function is currently known. We cloned 40 of the genes in Sbash’s genome with sizes ranging from 90 bp to 3,666 bp. We screened each gene for cytotoxicity and identified six genes that reduced growth of the host cells when expressed. We also screened for defense, the ability of each gene product to protect the host cell from infection by another phage. We identified eight Sbash gene products that defend host cells from infection by other mycobacteriophages. We have also analyzed genes in Mycobacteriophage Island3, a cluster I1 phage, for cytotoxicity and defense to complete the screen of this phage started by students in previous research groups.

Many plants possess medicinal properties. Some, such as the Pacific yew, have yielded chemotherapeutic drugs (taxanes). Scientists report that other extracts such as the leaves of Calendula officinalis (marigold), Vinca rosea (periwinkle), Viscum cruciatum (mistletoe), and Rosmarinus officinalis (rosemary) have anti-tumor activity. In most cases, the chemical components responsible for antiproliferative activity have not been identified and it is unclear if any individual components are as effective in isolation as they are in the context of the whole extract. Furthermore, in most cases, there are no data indicating whether these extracts have synergistic effects or cause negative reactions when used with other drugs. We are using HeLa (adenocarcinoma), RAW 264.7 (leukemia), HepG2 (hepatoma), MDA-MB-231 (adenocarcinoma), and human foreskin fibroblasts (HFF, non-tumorigenic) to test the antiproliferative activity of several plant extracts. We identified five extracts, grapeseed, guava, yew, juniper berry, and Vinca, that slow the growth of all five cell lines in a dose-dependent manner. We are using a variety of methods to understand the mechanism by which these extracts are blocking cell growth.

Rev1 is a Y family DNA polymerase that specializes in translesion DNA synthesis. Rev1 is unique in that it preferentially incorporates dCTP in the growing DNA strand, regardless of the templating base. This is because the template base is evicted from the active site and a template amino acid, arginine 324 (R324) acts as the template for the incoming dCTP. We hypothesize that arginine 324 and the neighboring leucine (L325) facilitate the eviction of the DNA template from the active site. To test this hypothesis, we worked to purify R324G/L325G Rev1 double mutant for the purpose of X-ray crystallographic examination of the protein-DNA-dNTP ternary complex. We transformed Escherichia coli (E. coli) and induced expression of both wild type Rev1 and R324G/L325G Rev1. The bacterial cells were lysed by sonification, and the lysate was purified with a GSTrap column. We were able to successfully isolate the Rev1 enzyme. Further purification and crystallization will be necessary to explore the x-ray crystal structure of R324G/L325G Rev1 protein.

We isolated and purified Tedro and BAjuniper which infect the host Microbacterium foliorium. Tedro is a lytic, cluster EF phage isolated from soil collected in Hawarden, Iowa. Its genome is 56,197 bp long, circularly permuted, and includes 83 protein-coding genes and no tRNA genes. We are examining two of Tedro’s genes, genes 56 and 57, both of which are predicted to encode a DnaE-like DNA polymerase III (alpha) in more detail. Tedro_57 is twice as large as Tedro_56 so we are using additional bioinformatic tools to understand these genes. BAjuniper was isolated from soil collected in a garden in Orange City, Iowa. Its genome is 41,985 bp long. It was assigned to cluster EB. BAjuniper’s genome includes one tRNA gene and we will finalize BAjuniper’s annotation shortly.

We annotated the genomes of four recently discovered Actinobacteriophages. Clayda5 and GShelby23 were isolated on Microbacterium foliorum NRRL B-24224. Clayda5 is a lytic, cluster EB phage, one of only 47 discovered to date. It has 10 base pair 3’ sticky overhanging ends and a GC content is 67.2%. It has 70 protein-coding genes and two tRNA genes in its 39,894 bp genome. Clayda5 was purified from soil collected in Hull, IA. GShelby23 was isolated from soil collected in Storm Lake, IA. It is a cluster EM phage, one of only six discovered to date. Its genome is circularly permuted and 53,603 bp long. Its GC content is 64.8%. Santhid and Wrigley are phages that infect Gordonia terrae 3612. Santhid is a cluster DY phage, one of only five discovered to date. It was isolated from soil collected in Orange City, IA. Its genome is 39,295 bp long and includes 60 protein-coding genes. Its GC content is 67.7% and has 10 base pair 3’ sticky overhanging ends. Wrigley was isolated using an enrichment protocol from soil collected in Johnston, IA. It is a cluster CY phage, one of only 17 discovered to date. It is a temperate phage whose genome is 51,878 bp long and includes 81 protein-coding genes. It has 10 base pair 3’ sticky overhanging ends and a GC content of 66.3%..