Alternative promoters and repetitive DNA elements define the species-dependent tissue-specific expression of the FMO1 genes of human and mouse.
ABSTRACT In humans, expression of the FMO1 (flavin-containing mono-oxygenase 1) gene is silenced postnatally in liver, but not kidney. In adult mouse, however, the gene is active in both tissues. We investigated the basis of this species-dependent tissue-specific transcription of FMO1. Our results indicate the use of three alternative promoters. Transcription of the gene in fetal human and adult mouse liver is exclusively from the P0 promoter, whereas in extra-hepatic tissues of both species, P1 and P2 are active. Reporter gene assays showed that the proximal P0 promoters of human (hFMO1) and mouse (mFmo1) genes are equally effective. However, sequences upstream (-2955 to -506) of the proximal P0 of mFmo1 increased reporter gene activity 3-fold, whereas hFMO1 upstream sequences (-3027 to -541) decreased reporter gene activity by 75%. Replacement of the upstream sequence of human P0 with the upstream sequence of mouse P0 increased activity of the human proximal P0 8-fold. Species-specific repetitive elements are present immediately upstream of the proximal P0 promoters. The human gene contains five LINE (long-interspersed nuclear element)-1-like elements, whereas the mouse gene contains a poly A region, an 80-bp direct repeat, an LTR (long terminal repeat), a SINE (short-interspersed nuclear element) and a poly T tract. The rat and rabbit FMO1 genes, which are expressed in adult liver, lack some (rat) or all (rabbit) of the elements upstream of mouse P0. Thus silencing of FMO1 in adult human liver is due apparently to the presence upstream of the proximal P0 of L1 (LINE-1) elements rather than the absence of retrotransposons similar to those found in the mouse gene.
Article: AVID: A global alignment program.[show abstract] [hide abstract]
ABSTRACT: In this paper we describe a new global alignment method called AVID. The method is designed to be fast, memory efficient, and practical for sequence alignments of large genomic regions up to megabases long. We present numerous applications of the method, ranging from the comparison of assemblies to alignment of large syntenic genomic regions and whole genome human/mouse alignments. We have also performed a quantitative comparison of AVID with other popular alignment tools. To this end, we have established a format for the representation of alignments and methods for their comparison. These formats and methods should be useful for future studies. The tools we have developed for the alignment comparisons, as well as the AVID program, are publicly available. See Web Site References section for AVID Web address and Web addresses for other programs discussed in this paper.Genome Research 02/2003; 13(1):97-102. · 13.61 Impact Factor
Article: Mammalian flavin-containing monooxygenases: structure/function, genetic polymorphisms and role in drug metabolism.[show abstract] [hide abstract]
ABSTRACT: Flavin-containing monooxygenase (FMO) oxygenates drugs and xenobiotics containing a "soft-nucleophile", usually nitrogen or sulfur. FMO, like cytochrome P450 (CYP), is a monooxygenase, utilizing the reducing equivalents of NADPH to reduce 1 atom of molecular oxygen to water, while the other atom is used to oxidize the substrate. FMO and CYP also exhibit similar tissue and cellular location, molecular weight, substrate specificity, and exist as multiple enzymes under developmental control. The human FMO functional gene family is much smaller (5 families each with a single member) than CYP. FMO does not require a reductase to transfer electrons from NADPH and the catalytic cycle of the 2 monooxygenases is strikingly different. Another distinction is the lack of induction of FMOs by xenobiotics. In general, CYP is the major contributor to oxidative xenobiotic metabolism. However, FMO activity may be of significance in a number of cases and should not be overlooked. FMO and CYP have overlapping substrate specificities, but often yield distinct metabolites with potentially significant toxicological/pharmacological consequences. The physiological function(s) of FMO are poorly understood. Three of the 5 expressed human FMO genes, FMO1, FMO2 and FMO3, exhibit genetic polymorphisms. The most studied of these is FMO3 (adult human liver) in which mutant alleles contribute to the disease known as trimethylaminuria. The consequences of these FMO genetic polymorphisms in drug metabolism and human health are areas of research requiring further exploration.Pharmacology [?] Therapeutics 07/2005; 106(3):357-87. · 8.56 Impact Factor
[show abstract] [hide abstract]
ABSTRACT: To determine the level of FMO1 protein present in human liver tissues, a monospecific antibody was prepared and a sensitive Western blotting procedure with enhanced chemiluminescence detection was developed. Human FMO1, purified from insect cells expressing the recombinant protein, was used as a protein standard for absolute quantification. The average concentrations of FMO1 in microsomes prepared from human liver, kidney, intestine, and fetal liver were found to be <1, 47 +/- 9, 2.9 +/- 1.9, and 14.4 +/- 3.5 pmol/mg, respectively. Quantitation in intestinal microsomes was complicated by variable degrees of proteolytic degradation of FMO1, not seen in microsomes prepared from liver or kidney. Recombinant human FMO1 and detergent-solubilized human duodenal microsomes both metabolized p-tolyl methyl sulfide stereoselectively to the (R)-sulfoxide, indicating the expression of functional FMO1 in human intestine. The relatively high levels of immunoquantifiable FMO1 in human kidney and fetal liver complement our previous catalytic studies in these tissues, which also demonstrated preferential (R)-p-tolyl methyl sulfoxide formation. These data demonstrate a profound ontogenic change in expression of hepatic FMO1 in humans, such that in adult life FMO1 is exclusively an extrahepatic drug-metabolizing enzyme. The marked expression levels of FMO1 found in human kidney coupled to the high catalytic activity of this isoform toward a diverse array of sulfides and tertiary amines suggest the possibility that human renal FMO1 is a significant contributor to the metabolic clearance of drugs and other xenobiotics bearing these functionalities.Drug Metabolism and Disposition 09/2000; 28(9):1107-11. · 3.73 Impact Factor