ABSTRACT
We screened soil samples for CO(2)-requiring extreme oligotrophs similar to Rhodococcus erythropolis N9T-4, which can grow on a basal salt agar medium without an organic carbon source. From 387 soil samples, three isolates were obtained and identified as Streptomyces spp. by 16S rDNA analysis. The isolates required gaseous CO(2) for growth and grew on a basal salt medium solidified by silica gel. These results suggest that such CO(2)-requiring oligotrophs occur widely in nature.
Subject(s)
Carbon Dioxide/metabolism , Soil Microbiology , Streptomyces/isolation & purification , Streptomyces/metabolism , Bacterial Typing Techniques , Base Sequence , Culture Media , DNA, Bacterial/analysis , DNA, Ribosomal/analysis , Molecular Sequence Data , RNA, Ribosomal, 16S/genetics , Streptomyces/geneticsABSTRACT
TIS11, a member of the CCCH zinc finger protein family, functions as a positive transcriptional regulator. TIS11 was localized in both the cytoplasm and nucleus when transiently expressed in COS-7 cells. Upon treatment with leptomycin B, a specific inhibitor of the nuclear export receptor CRM1, a marked nuclear accumulation of TIS11 was observed, indicating that TIS11 shuttles between the nucleus and the cytoplasm. By deletion studies using a green fluorescent protein fusion system, we have mapped a functional nuclear localization signal (NLS) to a region containing two tandem repeats of the zinc finger motif of TIS11. A site-directed mutagenesis analysis of TIS11 NLS has revealed the critical importance of two arginine residues (Arg127 and Arg131 in the rat TIS11). Furthermore, we demonstrated that the N-terminal Leu-rich region of TIS11 serves as an LMB-sensitive nuclear export signal (NES), indicating that TIS11 follows a CRM1-mediated export pathway. These results suggest that TIS11 is subject to constant nucleocytoplasmic shuttling due to its NLS and NES.
