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Full-Text Articles in Medicine and Health Sciences

Apobec3g Interacts With Ssdna By Two Modes: Afm Studies., Luda S. Shlyakhtenko, Samrat Dutta, Jaspreet Banga, Ming Li, Reuben S. Harris, Yuri L. Lyubchenko Oct 2015

Apobec3g Interacts With Ssdna By Two Modes: Afm Studies., Luda S. Shlyakhtenko, Samrat Dutta, Jaspreet Banga, Ming Li, Reuben S. Harris, Yuri L. Lyubchenko

Journal Articles: Pharmaceutical Sciences

APOBEC3G (A3G) protein has antiviral activity against HIV and other pathogenic retroviruses. A3G has two domains: a catalytic C-terminal domain (CTD) that deaminates cytidine, and a N-terminal domain (NTD) that binds to ssDNA. Although abundant information exists about the biological activities of A3G protein, the interplay between sequence specific deaminase activity and A3G binding to ssDNA remains controversial. We used the topographic imaging and force spectroscopy modalities of Atomic Force Spectroscopy (AFM) to characterize the interaction of A3G protein with deaminase specific and nonspecific ssDNA substrates. AFM imaging demonstrated that A3G has elevated affinity for deaminase specific ssDNA than for …


Samhd1 Is A Single-Stranded Nucleic Acid Binding Protein With No Active Site-Associated Nuclease Activity., Kyle J. Seamon, Zhiqiang Sun, Luda S. Shlyakhtenko, Yuri L. Lyubchenko, James T. Stivers Jul 2015

Samhd1 Is A Single-Stranded Nucleic Acid Binding Protein With No Active Site-Associated Nuclease Activity., Kyle J. Seamon, Zhiqiang Sun, Luda S. Shlyakhtenko, Yuri L. Lyubchenko, James T. Stivers

Journal Articles: Pharmaceutical Sciences

The HIV-1 restriction factor SAMHD1 is a tetrameric enzyme activated by guanine nucleotides with dNTP triphosphate hydrolase activity (dNTPase). In addition to this established activity, there have been a series of conflicting reports as to whether the enzyme also possesses single-stranded DNA and/or RNA 3'-5' exonuclease activity. SAMHD1 was purified using three chromatography steps, over which the DNase activity was largely separated from the dNTPase activity, but the RNase activity persisted. Surprisingly, we found that catalytic and nucleotide activator site mutants of SAMHD1 with no dNTPase activity retained the exonuclease activities. Thus, the exonuclease activity cannot be associated with any …


Remodeling Of Recg Helicase At The Dna Replication Fork By Ssb Protein., Zhiqiang Sun, Hui Yin Tan, Piero R. Bianco, Yuri L. Lyubchenko Apr 2015

Remodeling Of Recg Helicase At The Dna Replication Fork By Ssb Protein., Zhiqiang Sun, Hui Yin Tan, Piero R. Bianco, Yuri L. Lyubchenko

Journal Articles: Pharmaceutical Sciences

The RecG DNA helicase a key player in stalled replication fork rescue. The single-stranded DNA binding protein (SSB) participates in this process, but its role in the interaction of RecG with the fork remains unclear. We used atomic force microscopy (AFM) to visualize the interaction of RecG with a fork DNA in the presence of SSB. We discovered that SSB enhances RecG loading efficiency onto the DNA fork by threefold. Additionally, SSB interacts with RecG leading to the RecG remodeling. As a result, RecG separates from the fork, but remains bound to the DNA duplex. Moreover, in this new binding …


Bridged Filaments Of Histone-Like Nucleoid Structuring Protein Pause Rna Polymerase And Aid Termination In Bacteria., Matthew V. Kotlajich, Daniel R. Hron, Beth A. Boudreau, Zhiqiang Sun, Yuri L. Lyubchenko, Robert Landick Jan 2015

Bridged Filaments Of Histone-Like Nucleoid Structuring Protein Pause Rna Polymerase And Aid Termination In Bacteria., Matthew V. Kotlajich, Daniel R. Hron, Beth A. Boudreau, Zhiqiang Sun, Yuri L. Lyubchenko, Robert Landick

Journal Articles: Pharmaceutical Sciences

Bacterial H-NS forms nucleoprotein filaments that spread on DNA and bridge distant DNA sites. H-NS filaments co-localize with sites of Rho-dependent termination in Escherichia coli, but their direct effects on transcriptional pausing and termination are untested. In this study, we report that bridged H-NS filaments strongly increase pausing by E. coli RNA polymerase at a subset of pause sites with high potential for backtracking. Bridged but not linear H-NS filaments promoted Rho-dependent termination by increasing pause dwell times and the kinetic window for Rho action. By observing single H-NS filaments and elongating RNA polymerase molecules using atomic force microscopy, we …