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L1 and HERV-W retrotransposons are hypomethylated in human ovarian carcinomas.

Menendez L, Benigno BB, McDonald JF - Mol. Cancer (2004)

Bottom Line: We report the results of an preliminary examination of the methylation status of CpG dinucleotides associated with the L1 and HERV-W retrotransposons in benign and malignant human ovarian tumors.We find a reduction in the methylation of CpG dinucleotides within the promoter regions of these retroelements in malignant relative to non-malignant ovarian tissues.Consistent with these results, we find that relative L1 and HERV-W expression levels are elevated in representative samples of malignant vs. non-malignant ovarian tissues.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Genetics, University of Georgia, Life Science Building, Athens, GA 30602, USA. lmenen@uga.edu

ABSTRACT
Wide-spread hypomethylation of CpG dinucleotides is characteristic of many cancers. Retrotransposons have been identified as potential targets of hypomethylation during cellular transformation. We report the results of an preliminary examination of the methylation status of CpG dinucleotides associated with the L1 and HERV-W retrotransposons in benign and malignant human ovarian tumors. We find a reduction in the methylation of CpG dinucleotides within the promoter regions of these retroelements in malignant relative to non-malignant ovarian tissues. Consistent with these results, we find that relative L1 and HERV-W expression levels are elevated in representative samples of malignant vs. non-malignant ovarian tissues.

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Hypomethylation and expresion of L1 and HERV-W elements in ovarian cancer. Genomic DNA was digested either with MspI (left) or HpaII (right), and hybridized with probes specific for the promoter regions of L1 (A) or HERV-W (B) elements. The restriction enzymes MspI and HpaII recognize the sequence CCGG but HpaII only cuts when the recognition sequence is unmethylated at the inner cytosine (i.e., CCGG) while MspI is indifferent to the methylation status of the inner cytosine. Brackets indicate bands from restriction cut sites internal to the elements (B = benign cystic mass; LMP = low-malignancy potential or borderline tumor; N = normal ovary. (C) Real time RT-PCR was performed to determine expression levels of LINE-1 and HERV-W elements in representative malignant and non-malignant samples. Normalized values (retroelement expression value divided by expression value of the RPS27A control gene. Shown is the average of 3 replicate assays per sample ± SE. RPS27A expression has been previously determined to be unchanged between the malignant and non-malignant samples examined in this study (see text for details).
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Figure 1: Hypomethylation and expresion of L1 and HERV-W elements in ovarian cancer. Genomic DNA was digested either with MspI (left) or HpaII (right), and hybridized with probes specific for the promoter regions of L1 (A) or HERV-W (B) elements. The restriction enzymes MspI and HpaII recognize the sequence CCGG but HpaII only cuts when the recognition sequence is unmethylated at the inner cytosine (i.e., CCGG) while MspI is indifferent to the methylation status of the inner cytosine. Brackets indicate bands from restriction cut sites internal to the elements (B = benign cystic mass; LMP = low-malignancy potential or borderline tumor; N = normal ovary. (C) Real time RT-PCR was performed to determine expression levels of LINE-1 and HERV-W elements in representative malignant and non-malignant samples. Normalized values (retroelement expression value divided by expression value of the RPS27A control gene. Shown is the average of 3 replicate assays per sample ± SE. RPS27A expression has been previously determined to be unchanged between the malignant and non-malignant samples examined in this study (see text for details).

Mentions: Figure 1A &1B displays Southern blots of HpaI and MspI digested genomic DNA isolated from tissue samples and hybridized against probes homologous to regions encompassing the promoter regions of each family of elements. The HpaII/MspI restriction sites located within the promoter regions of both L1 and HERV-W elements are polymorphic among family members. By aligning the promoter regions of both families of elements present in the consensus human genome and identifying the HpaII/MspI sites present, we estimated that the expected size range of restriction fragments within the elements to be between ~100 – 700 bp and ~1500 – 3000 bp for L1 elements and between ~100 – 500 bp for HERV-W elements. Larger sized fragments representing partial digestions and/or polymorphic HpaII/MspI sites located within the elements or in regions flanking the elements are also visible.


L1 and HERV-W retrotransposons are hypomethylated in human ovarian carcinomas.

Menendez L, Benigno BB, McDonald JF - Mol. Cancer (2004)

Hypomethylation and expresion of L1 and HERV-W elements in ovarian cancer. Genomic DNA was digested either with MspI (left) or HpaII (right), and hybridized with probes specific for the promoter regions of L1 (A) or HERV-W (B) elements. The restriction enzymes MspI and HpaII recognize the sequence CCGG but HpaII only cuts when the recognition sequence is unmethylated at the inner cytosine (i.e., CCGG) while MspI is indifferent to the methylation status of the inner cytosine. Brackets indicate bands from restriction cut sites internal to the elements (B = benign cystic mass; LMP = low-malignancy potential or borderline tumor; N = normal ovary. (C) Real time RT-PCR was performed to determine expression levels of LINE-1 and HERV-W elements in representative malignant and non-malignant samples. Normalized values (retroelement expression value divided by expression value of the RPS27A control gene. Shown is the average of 3 replicate assays per sample ± SE. RPS27A expression has been previously determined to be unchanged between the malignant and non-malignant samples examined in this study (see text for details).
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC411053&req=5

Figure 1: Hypomethylation and expresion of L1 and HERV-W elements in ovarian cancer. Genomic DNA was digested either with MspI (left) or HpaII (right), and hybridized with probes specific for the promoter regions of L1 (A) or HERV-W (B) elements. The restriction enzymes MspI and HpaII recognize the sequence CCGG but HpaII only cuts when the recognition sequence is unmethylated at the inner cytosine (i.e., CCGG) while MspI is indifferent to the methylation status of the inner cytosine. Brackets indicate bands from restriction cut sites internal to the elements (B = benign cystic mass; LMP = low-malignancy potential or borderline tumor; N = normal ovary. (C) Real time RT-PCR was performed to determine expression levels of LINE-1 and HERV-W elements in representative malignant and non-malignant samples. Normalized values (retroelement expression value divided by expression value of the RPS27A control gene. Shown is the average of 3 replicate assays per sample ± SE. RPS27A expression has been previously determined to be unchanged between the malignant and non-malignant samples examined in this study (see text for details).
Mentions: Figure 1A &1B displays Southern blots of HpaI and MspI digested genomic DNA isolated from tissue samples and hybridized against probes homologous to regions encompassing the promoter regions of each family of elements. The HpaII/MspI restriction sites located within the promoter regions of both L1 and HERV-W elements are polymorphic among family members. By aligning the promoter regions of both families of elements present in the consensus human genome and identifying the HpaII/MspI sites present, we estimated that the expected size range of restriction fragments within the elements to be between ~100 – 700 bp and ~1500 – 3000 bp for L1 elements and between ~100 – 500 bp for HERV-W elements. Larger sized fragments representing partial digestions and/or polymorphic HpaII/MspI sites located within the elements or in regions flanking the elements are also visible.

Bottom Line: We report the results of an preliminary examination of the methylation status of CpG dinucleotides associated with the L1 and HERV-W retrotransposons in benign and malignant human ovarian tumors.We find a reduction in the methylation of CpG dinucleotides within the promoter regions of these retroelements in malignant relative to non-malignant ovarian tissues.Consistent with these results, we find that relative L1 and HERV-W expression levels are elevated in representative samples of malignant vs. non-malignant ovarian tissues.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Genetics, University of Georgia, Life Science Building, Athens, GA 30602, USA. lmenen@uga.edu

ABSTRACT
Wide-spread hypomethylation of CpG dinucleotides is characteristic of many cancers. Retrotransposons have been identified as potential targets of hypomethylation during cellular transformation. We report the results of an preliminary examination of the methylation status of CpG dinucleotides associated with the L1 and HERV-W retrotransposons in benign and malignant human ovarian tumors. We find a reduction in the methylation of CpG dinucleotides within the promoter regions of these retroelements in malignant relative to non-malignant ovarian tissues. Consistent with these results, we find that relative L1 and HERV-W expression levels are elevated in representative samples of malignant vs. non-malignant ovarian tissues.

Show MeSH
Related in: MedlinePlus