The human genome, like other mammalian genomes, encodes numerous natural antisense transcripts (NATs) that have been classified into head-to-head, tail-to-tail, or fully overlapped categories in reference to their sense transcripts. Evidence for NAT-mediated epigenetic silencing of sense transcription remains scanty. The DHRS4 gene encodes a metabolic enzyme and forms a gene cluster with its two immediately downstream homologous genes, DHRS4L2 and DHRS4L1 , generated by gene duplication. We identified a head-to-head NAT of DHRS4 , designated AS1DHRS4, which markedly regulates the expression of these three genes in the DHRS4 gene cluster. By pairing with ongoing sense transcripts, AS1DHRS4 not only mediates deacetylation of histone H3 and demethylation of H3K4 in cis for the DHRS4 gene, but also interacts physically in trans with the epigenetic modifiers H3K9- and H3K27-specific histone methyltransferases G9a and EZH2, targeting the promoters of the downstream DHRS4L2 and DHRS4L1 genes to induce local repressive H3K9me2 and H3K27me3 histone modifications. Furthermore, AS1DHRS4 induces DNA methylation in the promoter regions of DHRS4L2 by recruiting DNA methyltransferases. This study demonstrates that AS1DHRS4, as a long noncoding RNA, simultaneously controls the chromatin state of each gene within the DHRS4 gene cluster in a discriminative manner. This finding provides an example of transcriptional control over the multiple and highly homologous genes in a tight gene cluster, and may help explain the role of antisense RNAs in the regulation of duplicated genes as the result of genomic evolution.

Wiskott-Aldrich syndrome (WAS) and X-linked thrombocytopenia (XLT), caused by mutations of the WAS protein (WASP) gene, represent different phenotypes of the same disease. To demonstrate a phenotype/genotype correlation, we determined WASP gene mutations in 48 unrelated WAS families. Mutations included missense (20 families) and nonsense (eight) mutations located mostly in exons 1 to 4, and splice-site mutations (seven) and deletions and insertions (13) located preferentially in exons 7 to 11. Both genomic DNA and cDNA were sequenced and WASP expression was measured in cell lysates using peptide-specific rabbit anti-WASP antibodies. WASP was expressed in hematopoietic cell lines including bone marrow–derived CD34+ cells. Missense mutations located in exons 1 to 3 caused mild disease in all but one family and permitted WASP expression, although frequently at decreased concentration. Missense mutations affecting exon 4 were associated with classic WAS and, with one exception, barely detectable WASP. Nonsense mutations caused classic WAS and lack of protein. Insertions, deletions, and splice-site mutations resulted in classic WAS and absent, unstable, truncated, or multiply spliced protein. Using affinity precipitation, WASP was found to bind to Src SH3-containing proteins Fyn, Lck, PLC-γ, and Grb2, and mutated WASP, if expressed, was able to bind to Fyn-glutathione S-transferase (GST) fusion protein. We conclude that missense mutations affecting the PH domain (exons 1 to 3) of WASP inhibit less important functions of the protein and result in a mild phenotype, and that missense mutations affecting exon 4 and complex mutations affecting the 3′ portion of WASP interfere with crucial functions of the protein and cause classic WAS.

2,4‐Dichlorophenol hydroxylase 2,4‐Dichlorophenoxyacetate plasmid 2,4‐Dichlorophenoxyacetate degradation Alcaligenes eutrophus Pseudomonas putida