The promoter of the miR-200c/141 cluster is located in a CpG-rich region. (A) Analysis of the genomic region encompassing the miR-200c/141 cluster. Individual CpG dinucleotides are indicated by short vertical bars, the CpG island between positions -343 and -115 is represented by a dark grey box. Known ZEB1 binding sites  are marked with "▲". The degree of conservation among 17 mammalian species is shown in the middle part (area plot). In the lower part, the results of 5' Rapid Amplification of cDNA ends (5' RACE) experiments are depicted. Starting positions of clones representing different transcription start sites are indicated on the left, the number of identified clones indicated on the right side. (B) Luciferase reporter gene assays of empty vector (empty) (pMOD vector, Invivogen), a control insert lacking any promoter activity ((-) control) (intronic fraction of KIR3DL2 gene), an insert constituted by the GAPDH promoter ((+) control), and an insert encompassing positions -707 to +501 as indicated in (A). (C) Northern blot results using a U6 RNA, a miR-200c, and a miR-141 probe on RNA extracted from Hela cells transfected with pMOD empty vector or the pMOD vector containing the miR-200c/141 genomic region. Bands shown for the miRNAs correspond to the mature forms of miR-141 (22bp) and miR-200c (23bp).