In the case of MPA, the self-resistance mechanism has not been SBI-0206965 concentration elucidated. Figure 1 Role of IMPDH and MPA in GMP biosynthesis. MPA inhibits IMPDH. MPA: Mycophenolic acid. R: ribose 5′-monophosphate. IMP: inosine-5′-monophosphate, XMP: xanthosine-5′-monophosphate, guanosine-5′-monophosphate. GMP: Guanosine monophosphate. IMPDH: IMP dehydrogenase. The MPA biosynthetic gene cluster from Penicillium brevicompactum was identified only recently [12]. Interestingly, it turned out that the MPA gene cluster, in addition to the MPA biosynthetic genes, contains a putative IMPDH-encoding gene (mpaF). The study Belnacasan also revealed an additional putative IMPDH-encoding gene by probing the P. brevicompactum genomic

DNA [12]. A BLAST search using mpaF as query resulted in only a single IMPDH encoding gene per organism for all fully sequenced non-Penicillium

filamentous fungi (see the Results and Discussion section for details). Thus, the discovery of mpaF identifies P. brevicompactum as the first filamentous fungus known to feature two IMPDH encoding genes. In this study, we have identified additional species from the Penicillium subgenus Penicillium that contain two putative IMPDH encoding genes. Furthermore, we show that the two copies that are present in each fungus are dissimilar, and that one of them forms Luminespib cell line a new distinct group in a cladistic analysis. The IMPDH from the MPA cluster, mpaF, is the founding member of this novel group. The presence of mpaF within the biosynthesis cluster in P. brevicompactum hints at a role in MPA self-resistance. In this study, we examine this hypothesis and show that mpaF confers resistance to MPA when expressed in an otherwise highly sensitive non-producer

fungus Aspergillus nidulans. Results and discussion Expression of mpaF in A. nidulans confers resistance to MPA In order to investigate whether MpaFp from P. brevicompactum is resistant to MPA we transferred mpaF to a fungus, A. nidulans, which does not produce MPA. Specifically, we constructed a strain where the A. nidulans IMPDH Carteolol HCl structural gene (imdA) was replaced by the coding region of mpaF, see Figure 2A. The sensitivity of this strain towards MPA was then compared to a reference A. nidulans strain. As expected, the spot assays shown in Figure 2 demonstrate that the germination of WT spores is reduced due to MPA. This effect is most significant at media containing 100 and 200 μg/ml MPA where the viability is reduced by approximately two orders of magnitude as compared to the plate containing no MPA. The level of sensitivity of A. nidulans towards MPA is consistent with the toxic levels observed for other eukaryotic organisms [13, 14]. In contrast, MPA had little or no effect on spore viability of the strain NID495 where the gene encoding A. nidulans IMPDH (imdA) has been replaced by mpaF.