A Yeast Suppressor Screen Used To Identify Mammalian SIRT1 as a Proviral Factor for Middle East Respiratory Syndrome Coronavirus Replication.

Viral proteins must intimately interact with the host cell machinery during virus replication. Here, we used the yeast Saccharomyces cerevisiae as a system to identify novel functional interactions between viral proteins and eukaryotic cells. Our work demonstrates that when the Middle East respiratory syndrome coronavirus (MERS-CoV) ORF4a accessory gene is expressed in yeast it causes a slow-growth phenotype. ORF4a has been characterized as an interferon antagonist in mammalian cells, and yet yeast lack an interferon system, suggesting further interactions between ORF4a and eukaryotic cells. Using the slow-growth phenotype as a reporter of ORF4a function, we utilized the yeast knockout library collection to perform a suppressor screen where we identified the YDL042C/SIR2 yeast gene as a suppressor of ORF4a function. The mammalian homologue of SIR2 is SIRT1, an NAD-dependent histone deacetylase. We found that when SIRT1 was inhibited by either chemical or genetic manipulation, there was reduced MERS-CoV replication, suggesting that SIRT1 is a proviral factor for MERS-CoV. Moreover, ORF4a inhibited SIRT1-mediated modulation of NF-κB signaling, demonstrating a functional link between ORF4a and SIRT1 in mammalian cells. Overall, the data presented here demonstrate the utility of yeast studies for identifying genetic interactions between viral proteins and eukaryotic cells. We also demonstrate for the first time that SIRT1 is a proviral factor for MERS-CoV replication and that ORF4a has a role in modulating its activity in cells.IMPORTANCE Middle East respiratory syndrome coronavirus (MERS-CoV) initially emerged in 2012 and has since been responsible for over 2,300 infections, with a case fatality ratio of approximately 35%. We have used the highly characterized model system of Saccharomyces cerevisiae to investigate novel functional interactions between viral proteins and eukaryotic cells that may provide new avenues for antiviral intervention. We identify a functional link between the MERS-CoV ORF4a proteins and the YDL042C/SIR2 yeast gene. The mammalian homologue of SIR2 is SIRT1, an NAD-dependent histone deacetylase. We demonstrate for the first time that SIRT1 is a proviral factor for MERS-CoV replication and that ORF4a has a role in modulating its activity in mammalian cells.

Characterization of laser ultrasound source signals in biological tissues for imaging applications.

Short optical pulses emitted from a tunable Q-switched laser (800 to 2000 nm) generate laser ultrasound (LUS) signals at the surface of biological tissue. The LUS signal's acoustic frequency content, dependence on sample type, and optical wavelength are observed in the far field. The experiments yield a reference dataset for the design of noncontact LUS imaging systems. Measurements show that the majority of LUS signal energy in biological tissues is within the 0.5 and 3 MHz frequency bands and the total acoustic energy generated increases with the optical absorption coefficient of water, which governs tissue optical absorption in the infrared range. The experimental results also link tissue surface roughness and acoustic attenuation with limited LUS signal bandwidth in biological tissue. Images constructed using 810-, 1064-, 1550-, and 2000-nm generation laser wavelengths and a contact piezoelectric receiver demonstrates the impact of the generation laser wavelength on image quality. A noncontact LUS-based medical imaging system has the potential to be an effective medical imaging device. Such a system may mitigate interoperator variability associated with current medical ultrasound imaging techniques and expand the scope of imaging applications for ultrasound.