Selenium-dependent gene regulation in Archaea
Final Report Abstract
Selenium is an essential trace element for many members of all three domains of life, but how selenium is transported into cells is unknown. Selenium exerts its main biological function through the co-translationally inserted amino acid selenocysteine (Sec). The methanogenic archaeon Methanococcus maripaludis employs Sec-containing proteins in its central energy metabolism, hydrogenotrophic methanogenesis. However, when selenium is scarce, a set of seleniumindependent isoenzymes is induced, rendering growth independent of this trace element. However, which other selenium species are utilized by M. maripaludis, which other genes are regulated by selenium, how the cellular selenium status is sensed, and how this information is transduced to alter gene expression, is unknown. Previous studies indicated that selenophosphate, which is the biosynthetic precursor of Sec, directly or indirectly may represent the cellular selenium status. Furthermore, the LysR-type transcription regulator HrsM is involved in selenium-dependent gene regulation, but the mechanism of HrsM-dependent gene regulation is unknown. In order to gain better insight into selenium-dependent gene regulation in M. maripaludis, a comprehensive transcriptomic and proteomic analysis was conducted, which not only revealed the global seleniumdependent regulon of M. maripaludis but inspired further experimentation. Upon selenium depletion, various putative transporters were upregulated, which indicated the organism’s effort to tap into alternative sources of selenium. This led to demonstrating the use of nine new selenium sources M. maripaludis was previously not known to employ. Site-directed mutagenesis was employed, however unsuccessfully, to pinpoint the putative transporters’ physiological function. During our efforts to elucidate in vitro the mechanism of selenium-dependent repression of gene expression by HrsM, circumstantial evidence obtained suggests that the methodology employed leads to the protein’s unalterable DNA-binding activity. As a consequence, the working hypothesis as to the mode of HrsM’s function was adapted and will be experimentally probed in the future.
Publications
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Proteomic and transcriptomic analysis of selenium utilization in Methanococcus maripaludis. mSystems, 9(5).
Funkner, Katrina; Poehlein, Anja; Jehmlich, Nico; Egelkamp, Richard; Daniel, Rolf; von Bergen, Martin & Rother, Michael
