title: Cancer cells express aberrant DNMT3B transcripts encoding truncated proteins.
abstract: Cancer cells display an altered distribution of DNA methylation relative to normal cells. Certain tumor suppressor gene promoters are hypermethylated and transcriptionally inactivated, whereas repetitive DNA is hypomethylated and transcriptionally active. Little is understood about how the abnormal DNA methylation patterns of cancer cells are established and maintained. Here, we identify over 20 DNMT3B transcripts from many cancer cell lines and primary acute leukemia cells that contain aberrant splicing at the 5' end of the gene, encoding truncated proteins lacking the C-terminal catalytic domain. Many of these aberrant transcripts retain intron sequences. Although the aberrant transcripts represent a minority of the DNMT3B transcripts present, Western blot analysis demonstrates truncated DNMT3B isoforms in the nuclear protein extracts of cancer cells. To test if expression of a truncated DNMT3B protein could alter the DNA methylation patterns within cells, we expressed DNMT3B7, the most frequently expressed aberrant transcript, in 293 cells. DNMT3B7-expressing 293 cells have altered gene expression as identified by microarray analysis. Some of these changes in gene expression correlate with altered DNA methylation of corresponding CpG islands. These results suggest that truncated DNMT3B proteins could play a role in the abnormal distribution of DNA methylation found in cancer cells.
authors.affiliation: Section of Hematology/Oncology, Department of Medicine, University of Chicago, Chicago, IL 60637, USA.
authors.forename: K R
authors.initials: KR
authors.lastname: Ostler
authors.forename: E M
authors.initials: EM
authors.lastname: Davis
authors.forename: S L
authors.initials: SL
authors.lastname: Payne
authors.forename: B B
authors.initials: BB
authors.lastname: Gosalia
authors.forename: J
authors.initials: J
authors.lastname: Expósito-Céspedes
authors.forename: M M
authors.initials: MM
authors.lastname: Le Beau
authors.forename: L A
authors.initials: LA
authors.lastname: Godley
mesh_terms: D017398:Alternative Splicing; D015153:Blotting, Western; D002460:Cell Line; D045744:Cell Line, Tumor; D016000:Cluster Analysis; D018899:CpG Islands / Q000235:genetics; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics* / Q000378:metabolism; D019175:DNA Methylation; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D009369:Neoplasms / Q000235:genetics / Q000473:pathology; D020411:Oligonucleotide Array Sequence Analysis; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic; D014162:Transfection; D000097584:DNA Methyltransferase 3B
chemical_list: D004248:DNA (Cytosine-5-)-Methyltransferases; D020033:Protein Isoforms; D000097584:DNA Methyltransferase 3B