Doctor of Medicine, Jilin University (2008)
Andrew Hoffman, Postdoctoral Faculty Sponsor
Dysregulation of the insulin-like growth factor type I receptor (IGF1R) has been implicated in the progression and therapeutic resistance of malignancies. In acute myeloid leukemia (AML) cells, IGF1R is one of the most abundantly phosphorylated receptor tyrosine kinases, promoting cell growth through the PI3K/Akt signaling pathway. However, little is known regarding the molecular mechanisms underlying IGF1R gene dysregulation in cancer. We discovered a novel intragenic long noncoding RNA (lncRNA) within the IGF1R locus, named IRAIN, which is transcribed in an antisense direction from an intronic promoter. The IRAIN lncRNA was expressed exclusively from the paternal allele, with the maternal counterpart being silenced. Using both reverse transcription-associated trap and chromatin conformation capture assays, we demonstrate that this lncRNA interacts with chromatin DNA and is involved in the formation of an intrachromosomal enhancer/promoter loop. Knockdown of IRAIN lncRNA with shRNA abolishes this intrachromosomal interaction. In addition, IRAIN was downregulated both in leukemia cell lines and in blood obtained from high-risk AML patients. These data identify IRAIN as a new imprinted lncRNA that is involved in long-range DNA interactions.
View details for DOI 10.1093/nar/gku549
View details for PubMedID 25092925
Cancer progression is characterized by extensive tumor invasion into the surrounding extracellular matrix (ECM) and migration to metastatic sites. The increased proteolytic degradation of the ECM during tumor invasion is directly dependent on the activity of matrix metalloproteinases (MMPs), counter-balanced by tissue inhibitors of matrix metalloproteinases (TIMPs). In this study, we found that unbalanced expression of MMP/TIMP axis genes in tumors was correlated with aberrant epigenotypes in the various gene promoters. The malignant epigenotypes could be therapeutically corrected by a simple defined factor-mediated reprogramming approach. Correction of the abnormal epigenotypes by nuclear remodeling leads to a rebalance in the gene expression profile, an alteration in tumor cell morphology, attenuation of tumor cell migration and invasion in vitro, and reduced tumorigenicity in nude mice. We further identified the downregulation of the MKK-p38 MAPK signal pathway as an important underlying mechanism for reduced tumorigenicity in this epigenetic reprogramming model. These data demonstrate that the malignant phenotypes seen in cancer can be corrected by a nuclear remodeling mechanism, thus highlighting a novel non-chemotherapeutic, non-radiotherapeutic approach for the treatment of cancer.
View details for DOI 10.1002/ijc.28487
View details for Web of Science ID 000329579500007
View details for PubMedID 24105737
Kcnq1ot1 is a long noncoding ribonucleic acid (RNA; lncRNA) that participates in the regulation of genes within the Kcnq1 imprinting domain. Using a novel RNA-guided chromatin conformation capture method, we demonstrate that the 5' region of Kcnq1ot1 RNA orchestrates a long-range intrachromosomal loop between KvDMR1 and the Kcnq1 promoter that is required for maintenance of imprinting. PRC2 (polycomb repressive complex 2), which participates in the allelic repression of Kcnq1, is also recruited by Kcnq1ot1 RNA via EZH2. Targeted suppression of Kcnq1ot1 lncRNA prevents the creation of this long-range intrachromosomal loop and causes loss of Kcnq1 imprinting. These observations delineate a novel mechanism by which an lncRNA directly builds an intrachromosomal interaction complex to establish allele-specific transcriptional gene silencing over a large chromosomal domain.
View details for DOI 10.1083/jcb.201304152
View details for Web of Science ID 000329347100007
View details for PubMedID 24395636
Targeted gene silencing is an important approach in both drug development and basic research. However, the selection of a potent suppressor has become a significant hurdle to implementing maximal gene inhibition for this approach. We attempted to construct a 'super suppressor' by combining the activities of two suppressors that function through distinct epigenetic mechanisms.Gene targeting vectors were constructed by fusing a GAL4 DNA-binding domain with a epigenetic suppressor, including CpG DNA methylase Sss1, histone H3 lysine 27 methylase vSET domain, and Kruppel-associated suppression box (KRAB). We found that both Sss1 and KRAB suppressors significantly inhibited the expression of luciferase and copGFP reporter genes. However, the histone H3 lysine 27 methylase vSET did not show significant suppression in this system. Constructs containing both Sss1 and KRAB showed better inhibition than either one alone. In addition, we show that KRAB suppressed gene expression by altering the histone code, but not DNA methylation in the gene promoter. Sss1, on the other hand, not only induced de novo DNA methylation and recruited Heterochromatin Protein 1 (HP1a), but also increased H3K27 and H3K9 methylation in the promoter.Epigenetic studies can provide useful data for the selection of suppressors in constructing therapeutic vectors for targeted gene silencing.
View details for DOI 10.1186/1756-8935-7-20
View details for PubMedID 25184003
RUNX1, a master regulator of hematopoiesis, is the most commonly perturbed target of chromosomal abnormalities in hematopoietic malignancies. The t(8;21) translocation is found in 30-40% of cases of acute myeloid leukemia (AML). Recent whole-exome sequencing also reveals mutations and deletions of RUNX1 in some solid tumors. We describe a RUNX1-intragenic long noncoding RNA RUNXOR that is transcribed as unspliced transcript from an upstream overlapping promoter. RUNXOR was upregulated in AML samples and in response to Ara-C treatment in vitro. RUNXOR utilizes its 3'-terminal fragment to directly interact with the RUNX1 promoter and enhancers and participates in the orchestration of an intrachromosomal loop. The 3' region of RUNXOR also participates in long-range interchromosomal interactions with chromatin regions that are involved in multiple RUNX1 translocations. These data suggest that RUNXOR noncoding RNA may function as a previously unidentified candidate component that is involved in chromosomal translocation in hematopoietic malignancies.
View details for DOI 10.1002/ijc.28922
View details for PubMedID 24752773
Generation of induced pluripotent stem cells (iPSCs) by defined factors is an extremely inefficient process, because there is a strong epigenetic block preventing cells from achieving pluripotency. Here we report that virally expressed factors bound to the promoters of their target genes to the same extent in both iPSCs and unreprogrammed cells (URCs). However, expression of endogenous pluripotentcy genes was observed only in iPSCs. Comparison of local chromatin structure of the OCT4 locus revealed that there was a cohesin-complex-mediated intrachromosomal loop that juxtaposes a downstream enhancer to the gene's promoter, enabling activation of endogenous stemness genes. None of these long-range interactions were observed in URCs. Knockdown of the cohesin-complex gene SMC1 by RNAi abolished the intrachromosomal interaction and affected pluripotency. These findings highlight the importance of the SMC1-orchestrated intrachromosomal loop as a critical epigenetic barrier to the induction of pluripotency.
View details for DOI 10.1016/j.stem.2013.05.012
View details for Web of Science ID 000329570100010
View details for PubMedID 23747202