Further evidence that is consistent with this idea is the fact that for 30% of the iESTs, at least one EST sequenced from stress libraries corresponding to the same gene did not retain the intronic sequences, i.e., the corresponding mRNA was correctly processed (Additional file 1). The Sepantronium purchase spliceosome genes are not repressed under heat shock and cadmium stress The inhibition of mRNA splicing caused by heat shock and cadmium treatment could be due to a decrease in the expression of genes encoding

proteins of the spliceosome complex, leading to a reduction in the levels of the proteins forming the spliceosome. To test this hypothesis we identified all genes coding for spliceosome proteins that were present in B. emersonii EST database [19, 22, 23]. We observed 41 distinct genes (corresponding to 91 ESTs) encoding proteins involved in mRNA processing in this fungus (Additional file 2). To verify if these genes were up- or down-regulated during stress, we used the expression profile beta-catenin inhibitor data of Tipifarnib concentration microarray assays of B. emersonii cells submitted to cadmium and heat shock, previously published by our group [19]. Among the 41 genes of B. emersonii related to mRNA processing, 29 were present on the microarray slide and only two of them were shown to be differentially expressed in response to cadmium or heat shock. One was induced

by heat shock (BeE60H22E01 – snRNP core protein SMX5d) and the other (BeE60N15H01 – putative small nuclear ribonucleoprotein Sm-D1) was repressed by cadmium treatment [19, 23]. The 41 genes observed through our search certainly

do not correspond to all genes involved in mRNA processing in B. emersonii, since it has been shown that the spliceosome machinery is formed by hundreds of proteins in eukaryotes [2]. below However, we believe that our set of genes is a significant part of those that encode proteins of the mRNA processing complex in B. emersonii. Nevertheless, we observed that only one gene was repressed under stress conditions. Thus, our data suggest that inhibition of mRNA splicing after cadmium and heat stress in this fungus is not due to a global repression of the genes involved in the splicing process under these conditions. One of the possible effects of cadmium that lead to toxicity in cells is its capacity of displace zinc (Zn2+) and calcium (Ca2+) from proteins that need these cations to perform their functions [16, 34, 35]. So, the inhibition of splicing by cadmium in B. emersonii could be due to the substitution of zinc in proteins involved in mRNA processing, which could lead to impairment or even to loss of their function. Considering this hypothesis, we evaluated if among B. emersonii spliceosome proteins there were some that possessed zinc-binding domains, as zinc finger or zinc-related motifs, which could be affected by the presence of cadmium inside the cells.