Dataset Information

Tet Enzymes, Variants, and Differential Effects on Function.

ABSTRACT: Discovery of the ten-eleven translocation 1 (TET) methylcytosine dioxygenase family of enzymes, nearly 10 years ago, heralded a major breakthrough in understanding the epigenetic modifications of DNA. Initially described as catalyzing the oxidation of methyl cytosine (5mC) to hydroxymethyl cytosine (5hmC), it is now clear that these enzymes can also catalyze additional reactions leading to active DNA demethylation. The association of TET enzymes, as well as the 5hmC, with active regulatory regions of the genome has been studied extensively in embryonic stem cells, although these enzymes are expressed widely also in differentiated tissues. However, TET1 and TET3 are found as various isoforms, as a result of utilizing alternative regulatory regions in distinct tissues. Some of these isoforms, like TET2, lack the CXXC domain which probably has major implications on their recruitment to specific loci in the genome, while in certain contexts TET1 is seen paradoxically to repress transcription. In this review we bring together these novel aspects of the differential regulation of these Tet isoforms and the likely consequences on their activity.

SUBMITTER: Melamed P

PROVIDER: S-EPMC5844914 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Tet Enzymes, Variants, and Differential Effects on Function.

Melamed Philippa P Yosefzon Yahav Y David Cfir C Tsukerman Anna A Pnueli Lilach L

Frontiers in cell and developmental biology 20180305

Discovery of the ten-eleven translocation 1 (TET) methylcytosine dioxygenase family of enzymes, nearly 10 years ago, heralded a major breakthrough in understanding the epigenetic modifications of DNA. Initially described as catalyzing the oxidation of methyl cytosine (5mC) to hydroxymethyl cytosine (5hmC), it is now clear that these enzymes can also catalyze additional reactions leading to active DNA demethylation. The association of TET enzymes, as well as the 5hmC, with active regulatory regio ...[more]

PMID: 29556496

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Project description:ObjectivesVariants of the secreted glycoprotein, proprotein convertase subtilisin/kexin 9 (PCSK9), associate with both hypo- and hyper-cholesterolemic phenotypes. Herein, we carried out full exonic sequencing of PCSK9 documenting the frequency of single and multiple PCSK9 variations and their effects on serum lipoprotein and PCSK9 levels in Caucasian Canadians.MethodsThe 12 exons of PCSK9 were sequenced in 207 unrelated Caucasian Canadians. Minor allele frequencies of PCSK9 variants were compared amongst LDL cholesterol (LDLC) quintiles. Serum PCSK9 levels were measured by ELISA and lipoproteins by enzymatic methods. Comparisons were made with a Caucasian family cohort (n=51) and first generation African Canadians (n=31).ResultsIn Caucasians, but not African Canadians, the c.61_63insCTG (denoted L10Ins) and A53V PCSK9 variations were linked and their frequency was significantly higher among Caucasian Canadians with LDLC levels in the <25th percentile. In both the unrelated and family Caucasian cohorts those carrying the L10A53V PCSK9 variant had significantly lower LDLC without reduction in plasma PCSK9. The I474V PCSK9 variant associated with significantly lower serum PCSK9 and LDLC. A novel PCSK9 variant was identified; E206K. We found that the frequency of multiple PCSK9 variations was higher in first generation African Canadians.ConclusionsWe showed that the L10A53V and I474V PCSK9 variants were significantly associated with lower LDLC levels in Caucasian Canadians but differed in their effect on serum PCSK9 concentrations, illuminating differences in their mechanism of inaction and indicating that that PCSK9 measurement alone may not always be a good indicator of PCSK9 function.Full exonic sequencing of PCSK9 pointed to factors that may contribute to L10Ins PCSK9 variant loss of function in Canadians of Caucasian but not those of African descent. These included; (1) its tight linkage with the A53V variant in Caucasians and/or (2) for both the L10 and I474V, the combined (and negating) effect of multiple, differing phenotypic PCSK9 variants within individuals of African ancestry for which combinations of PCSK9 variations and their overall frequency was higher. No population studies, to our knowledge, have addressed or accessed the effect of multiple PCSK9 variants on cholesterol profiles. Our results indicate that this should be considered.

Dataset Information

Tet Enzymes, Variants, and Differential Effects on Function.

Publications

Tet Enzymes, Variants, and Differential Effects on Function.

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