title: Suppression of p21 by c-Myc through members of miR-17 family at the post-transcriptional level.
abstract: The miR-17 family, composed of miR-17-5p, miR-20a/b, miR-106a/b and miR-93, has been demonstrated to take part in critical pathways that regulate cellular life and death decisions during normal development and in malignancy. Previous studies have shown that the expression of miR-17 family members has close relationship with the expression of c-Myc. Another study has reported p21 is a direct target of miR-17 family and their silencing of p21 contributes to tumor cell proliferation in part. Since c-Myc is a potent transcriptional repressor of p21, these findings suggest that c-Myc may negatively modulate p21 expression through an additional pathway except transcriptional suppression. In the study presented here, we compared p21 mRNA in the nucleus and cytoplasm of c-Myc stable transfectants with its control, which indicated further repression of p21 by c-Myc at the post-transcriptional level. Stem-loop and conventional real-time PCR showed elevated expression of some members in miR-17 family and their primary transcripts when c-Myc was stably overexpressed. To further investigate the relationship of c-Myc, miR-17 family and p21, we antagonized the expression of each miR-17 family member by transfection of their antisense oligonucleotides respectively in transfectants constitutively overexpressing c-Myc or not, and found that the restoration of p21 expression by treatment above was much stronger in the presence of c-Myc. These results suggest c-Myc could further repress p21 expression at the post-transcriptional level through some, but not all, members of miR-17 family.
authors.affiliation: Laboratory of Cell and Molecular Biology & State Key Laboratory of Molecular Oncology, Cancer Institute & Cancer Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100021, PR China.
authors.forename: Zaozao
authors.initials: Z
authors.lastname: Wang
authors.forename: Mei
authors.initials: M
authors.lastname: Liu
authors.forename: Hongxia
authors.initials: H
authors.lastname: Zhu
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.forename: Shun
authors.initials: S
authors.lastname: He
authors.forename: Chenfei
authors.initials: C
authors.lastname: Hu
authors.forename: Lanping
authors.initials: L
authors.lastname: Quan
authors.forename: Jinfeng
authors.initials: J
authors.lastname: Bai
authors.forename: Ningzhi
authors.initials: N
authors.lastname: Xu
mesh_terms: D001483:Base Sequence; D015153:Blotting, Western; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000096:biosynthesis* / Q000235:genetics; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics*; D057809:HEK293 Cells; D006801:Humans; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; C524941:MIRN17 microRNA, human; C489427:MYC protein, human; D035683:MicroRNAs; D016271:Proto-Oncogene Proteins c-myc