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Pathogenic germline mutations in the folliculin (FLCN) tumor suppressor gene predispose to Birt–Hogg–Dubé (BHD) syndrome, a rare disease characterized by the development of cutaneous hamartomas (fibrofolliculomas), multiple lung cysts, spontaneous pneumothoraces and renal cell cancer. In this study, we report the identification of 13 variants and three polymorphisms in the FLCNgene in 143 Danish patients or families with suspected BHD syndrome. Functional mini-gene splicing analysis revealed that two intronic variants (c.1062+2T>G and c.1177-5_1177-3del) introduced splicing aberrations. Eleven families exhibited the c.1062+2T>G mutation. Combined single nucleotide polymorphism array-haplotype analysis showed that these families share a 3-Mb genomic fragment containing the FLCNgene, revealing that the c.1062+2T>G mutation is a Danish founder mutation. On the basis of in silicoprediction and functional splicing assays, we classify the 16 identified variants in the FLCNgene as follows: nine as pathogenic, one as likely pathogenic, three as likely benign and three as polymorphisms. In conclusion, the study describes the FLCNmutation spectrum in Danish BHD patients, and contributes to a better understanding of BHD syndrome and management of BHD patients.

Localized mRNAs are transported to sites of local protein synthesis in large ribonucleoprotein (RNP) granules, but their molecular composition is incompletely understood. Insulin-like growth factor II mRNA-binding protein (IMP) zip code-binding proteins participate in mRNA localization, and in motile cells IMP-containing granules are dispersed around the nucleus and in cellular protrusions. We isolated the IMP1-containing RNP granules and found that they represent a unique RNP entity distinct from neuronal hStaufen and/or fragile X mental retardation protein granules, processing bodies, and stress granules. Granules were 100–300 nm in diameter and consisted of IMPs, 40 S ribosomal subunits, shuttling heterologous nuclear RNPs, poly(A)-binding proteins, and mRNAs. Moreover granules contained CBP80 and factors belonging to the exon junction complex and lacked eIF4E, eIF4G, and 60 S ribosomal subunits, indicating that embodied mRNAs are not translated. Granules embodied mRNAs corresponding to about 3% of the human embryonic kidney 293 mRNA transcriptome. Messenger RNAs encoding proteins participating in the secretory pathway and endoplasmic reticulum-associated quality control, as well as ubiquitin-dependent metabolism, were enriched in the granules, reinforcing the concept of RNP granules as post-transcriptional operons.

Localized mRNAs are transported to sites of local protein synthesis in large ribonucleoprotein (RNP) granules, but their molecular composition is incompletely understood. Insulin-like growth factor II mRNA-binding protein (IMP) zip code-binding proteins participate in mRNA localization, and in motile cells IMP-containing granules are dispersed around the nucleus and in cellular protrusions. We isolated the IMP1-containing RNP granules and found that they represent a unique RNP entity distinct from neuronal hStaufen and/or fragile X mental retardation protein granules, processing bodies, and stress granules. Granules were 100–300 nm in diameter and consisted of IMPs, 40 S ribosomal subunits, shuttling heterologous nuclear RNPs, poly(A)-binding proteins, and mRNAs. Moreover granules contained CBP80 and factors belonging to the exon junction complex and lacked eIF4E, eIF4G, and 60 S ribosomal subunits, indicating that embodied mRNAs are not translated. Granules embodied mRNAs corresponding to about 3% of the human embryonic kidney 293 mRNA transcriptome. Messenger RNAs encoding proteins participating in the secretory pathway and endoplasmic reticulum-associated quality control, as well as ubiquitin-dependent metabolism, were enriched in the granules, reinforcing the concept of RNP granules as post-transcriptional operons.

The promoter of the cholecystokinin (CCK) gene possesses evolutionary conserved juxtaposed E‐box and cAMP/TPA responsive elements (CRE/TRE). We have examined the functional interaction of these two sites. As previously noted, c‐Jun/c‐Fos heterodimers greatly increase promoter activity through association with the CRE/TRE. Mutation of the E‐box enhanced the activation by c‐Jun/c‐Fos, as well as stimulation by forskolin and bFGF, that acts through the CRE/TRE site. Moreover, c‐Jun/c‐Fos stimulation was inhibited by co‐expression of c‐Myc and Max. The results indicate that factors associating with the E‐box exhibit a negative cooperative effect on the activation via the CRE/TRE element. We propose that this mechanism plays a significant role in CCK gene transcription and other genes with juxtaposed E‐box and CRE/TRE.