The shewanellae are aquatic microorganisms with worldwide distribution. Their hallmark features include unparalleled respiratory diversity and the capacity to thrive at low temperatures. As a genus the shewanellae are physiologically diverse, and this review provides an overview of the varied roles they serve in the environment and describes what is known about how they might survive in such extreme and harsh environments. In light of their fascinating physiology, these organisms have several biotechnological uses, from bioremediation of chlorinated compounds, radionuclides, and other environmental pollutants to energy-generating biocatalysis. The ecology and biotechnology of these organisms are intertwined, with genomics playing a key role in our understanding of their physiology.

No abstract

No abstract

AU-rich elements (AREs) in the 3' untranslated region (UTR) of numerous mammalian transcripts function as instability elements that promote rapid mRNA degradation. Tristetraprolin (TTP) is an ARE-binding protein that promotes rapid mRNA decay through mechanisms that are poorly understood. A 31 nucleotide ARE sequences from the TNF-alpha 3' UTR promoted TTP-dependent mRNA decay when it was inserted into the 3' UTR of a beta-globin reporter transcript, indicating that this short sequence was sufficient for TTP function. We used a gel shift assay to identify a TTP-containing complex in cytoplasmic extracts from TTP-transfected HeLa cells that bound specifically to short ARE sequences. This TTP-containing complex also contained the 5'-3' exonuclease Xrn1 and the exosome component PM-scl75 because it was super-shifted with anti-Xrn1 or anti-PMscl75 antibodies. RNA affinity purification verified that these proteins associated specifically with ARE sequences in a TTP-dependent manner. Using a competition binding assay, we found that the TTP-containing complex bound with high affinity to short ARE sequences from GM-CSF, IL-3, TNF-alpha, IL-2, and c-fos, but did not bind to a U-rich sequence from c-myc, a 22 nucleotide poly U sequence or a mutated GM-CSF control sequence. High affinity binding by the TTP-containing complex correlated with TTP-dependent deadenylation and decay of capped, polyadenylated transcripts in a cell-free mRNA decay assay, suggesting that the TTP-containing complex was functional. These data support a model whereby TTP functions to enhance mRNA decay by recruiting components of the cellular mRNA decay machinery to the transcript.