It was recently found that a mixture of nine amino acids down-regulate Clostridium difficile toxin production when added to peptone yeast extract (PY) cultures of strain VPI 10463 (S. Karlsson, L. G. Burman, and T. Åkerlund, Microbiology 145:1683-1693, 1999). In the present study, seven of these amino acids were found to exhibit a moderate suppression of toxin production, whereas proline and particularly cysteine had the greatest impact, on both reference strains (n ‫؍‬ 6) and clinical isolates (n ‫؍‬ 28) of C. difficile (>99% suppression by cysteine in the highest toxin-producing strain). Also, cysteine derivatives such as acetylcysteine, glutathione, and cystine effectively down-regulated toxin expression. An impact of both cysteine and cystine but not of thioglycolate on toxin yield indicated that toxin expression was not regulated by the oxidation-reduction potential. Several metabolic pathways, including butyric acid and butanol production, were coinduced with the toxins in PY and down-regulated by cysteine. The enzyme 3-hydroxybutyryl coenzyme A dehydrogenase, a key enzyme in solventogenesis in Clostridium acetobutylicum, was among the most up-regulated proteins during high toxin production. The addition of butyric acid to various growth media induced toxin production, whereas the addition of butanol had the opposite effect. The results indicate a coupling between specific metabolic processes and toxin expression in C. difficile and that certain amino acids can alter these pathways coordinately. We speculate that down-regulation of toxin production by the administration of such amino acids to the colon may become a novel approach to prophylaxis and therapy for C. difficile-associated diarrhea.

Herpes simplex virus (HSV) immediate-early protein ICP27 is a multifunctional regulator of viral and cellular gene expression. It has previously been shown that ICP27 directly or indirectly modulates several posttranscriptional processes, such as pre-mRNA splicing and polyadenylation. We show here that pre-mRNA splicing is inhibited in nuclear extracts prepared from cells in which ICP27 has been transiently expressed. Our results show that splicing inhibition in ICP27 extracts is manifested at early stages of the splicing process. Furthermore, our results suggest that an enzymatic activity in ICP27-containing extracts causes the splicing inhibition.

SR protein ASF/SF2 is a general pre-mRNA splicing factor as well as a regulator of alternative splicing. Data presented here show that ASF/SF2 is efficiently recruited to sites in the nucleus where adenovirus genes are transcribed and the resulting pre-mRNAs are processed. At the intermediate stages of a productive infection, ASF/SF2 colocalizes with small nuclear ribonucleoprotein particles (snRNPs), splicing factors in ring-like structures surrounding viral replication centres and, at late stages of the infection, in enlarged speckles. Results presented here demonstrate that ASF/SF2 requires only one of the two RNA-recognition motifs (RRMs) present in the protein for its efficient recruitment to the ring-like structures, where viral pre-mRNAs are transcribed and processed, and that the arginine/serine-rich (RS) domain in ASF/SF2 is both redundant and insufficient for the translocation of the protein to active viral RNA polymerase II genes in adenovirus-infected cells.Human adenovirus type 5 (family Adenoviridae, genus Mastadenovirus) is a non-enveloped icosahedral virus containing a linear double-stranded DNA molecule that replicates in the cell nucleus. In a productive adenovirus infection there is a dramatic reorganization of the cell nucleus during the intermediate and late stages of lytic infection. At intermediate stages, essential pre-mRNA splicing factors, e.g. snRNPs, which are normally evenly distributed over the entire nucleoplasm, and concentrated in so-called splicing speckles, become concentrated in ringlike structures surrounding viral replication centres (also referred to as peripheral replicative zones) (Bridge et al., 1993(Bridge et al., , 1995. Virus-induced ring-like structures represent nuclear sites where newly replicated adenovirus DNA is heavily transcribed by RNA Pol II and where the resulting pre-mRNAs are processed (Pombo et al., 1994). At the late stages of lytic infection, splicing factors are further redistributed into sites that resemble enlarged speckles, situated relatively distant from viral replication centres. This type of structure in adenovirus-infected cells has been shown to contain snRNPs and spliced adenovirus mRNAs (Bridge et al., 1996).Immunolocalization studies of adenovirus-infected cells have shown that the SR protein family of splicing factors is redistributed as a consequence of adenovirus infection. Although these studies clearly indicated that the vast majority of SR proteins are dramatically relocalized in adenovirus-infected cells, they did not address how individual SR proteins are affected (Bridge et al., 1995). The present study was initiated in order to study how SR protein ASF/SF2 is distributed during the course of a lytic adenovirus infection in cultured cells. SR proteins are essential splicing factors and regulators of alternative pre-mRNA splicing (reviewed by Graveley, 2000). All SR proteins have a modular organization containing an N-terminal RNA-binding domain consisting of either one or two RRMs, and a C-terminal domain RS domain containing repe...

In recent Swedish studies of Scandinavian pre-Christian religion of the late Iron Age, various scholars have questioned the utility of the concept of religion in this field. According to these scholars, the concept of religion obscures the specific character of religions of the small-scale non-literate societies of the pre-Christian Age. In the article, I critically examine suggestions that we abandon the academic concept of religion and replace it with an emic concept, or a concept derived from an emic context. I further argue that this strategy implies an inappropriate dualistic opposition between Scandinavian pre-Christian religion and so-called world religions. I conclude with a critical evaluation of problematic formulations of religious change and variation, presented by the same scholars who criticize the use of the academic category of religion. I try to draw attention to certain problematic implications of these demands. I conclude that we should continue to employ the concept of religion in connection with the religious worlds of pre-Christian societies. The strategy proposed by these scholars may turn out to be merely one more way of imposing misconceptions on this period.