For invasion assays, the upper chamber was pre-coated with Matrigel (BD Biosciences), and 2??104 QGY-7703 cells or Huh7 cells were seeded onto the upper chamber. In vivo metastasis assay Male nude mice were purchased from your Institute of Materia Medica (CAS, Shanghai, China) and cared for in accordance with the National Institutes of Health Guideline for the Care and Use of Laboratory Animals. stability and TGF-1 expression. Introduction ADP-ribosylation is an evolutionarily conserved post-translational KBU2046 modification that plays important roles in expanding the range of cellular functions, such as DNA repair and replication, chromatin remodeling, transcription, and telomere homeostasis1,2. ADP-ribosylation is mainly catalyzed by intracellular ADP-ribosyltransferases (ARTs), which use nicotinamide adenine dinucleotide (NAD+) to transfer ADP-ribose moieties to specific residues on KBU2046 target proteins, leading to mono-ADP-ribosylation (MARylation) or the formation of linear or branched chains of poly-ADP-ribose (PARylation)1,2. The functions of PARylation are relatively well characterized, and its inhibitors have been extensively investigated for the treatment of numerous malignancy types, especially in ovarian malignancy and breast malignancy including BRCA1/2 Rabbit Polyclonal to ARX mutation3,4. In KBU2046 contrast to PARylation, the specific functions of MARylation are much less comprehended. MARylation is usually involved in transcriptional regulation, unfolded protein response, DNA repair, insulin secretion, immunity, and malignancy development5C7. In mammals, at least 16 ADP-ribosyltransferases, including the cholera toxin-like ART family, the majority of the diphtheria toxin-like ART (ARTD) family, and some of the sirtuin family, catalyze MARylation8. Poly(ADP-ribose) polymerase 12 (PARP12), also known as ARTD12, is usually a mono-ADP-ribosyltransferase. It was originally identified as a putative antiviral gene belonging to a large family of interferon-stimulated genes whose expression is usually often induced during viral infections9,10. PARP12 expression is also induced by bacterial superantigen-(SEB)-mediated harmful shock11,12. PARP12 contains five common CCCH zinc fingers, two WWE domains, and a catalytic domain name11,13. The zinc fingers of PARP12 are associated with viral and cytoplasmic RNAs14. PARP12 can translocate to cytoplasmic stress granules in response to stress, which is dependent on its WWE domain name association with poly-ADP-ribose polymers catalyzed by PARP115. PARP12 also inhibits cellular translation and computer virus replication by directly binding to the polysomes of Venezuelan equine encephalitis-infected cells10,12. However, the function of PARP12 in malignancy development remains largely unknown. In the present study, we found that PARP12 is usually associated with FHL2 and implicated in the regulation of its stability, thereby negatively regulating TGF-1 expression and EMT processes. PARP12 deficiency promotes the migration and invasion of HCC cells and increases HCC metastasis in vivo. Our results indicated that PARP12 is usually a tumor suppressor and may be a novel therapeutic option for HCC treatment. Results PARP12 interacts with FHL2 To identify the functional partners of PARP12, we generated HEK293T cells that stably expressed streptavidin-Flag-S protein (SFB)-tagged PARP12 and conducted tandem affinity purification. Mass spectrometry analysis revealed that FHL2, a LIM-only protein that belongs to the four-and-a-half LIM-only protein family, was present in the PARP12 affinity purification complex (Fig.?1a). Then, we performed exogenous and endogenous reciprocal immunoprecipitation (IP) assays to validate the conversation between PARP12 and FHL2. As shown in Fig.?1b, c, the exogenously expressed HA-tagged FHL2 interacted with SFB-tagged PARP12, and GFP-tagged PARP12 interacted with SFB-tagged FHL2. Next, we examined the conversation of endogenous PARP12 and FHL2 in HEK293T, QGY-7703, and Huh7 cells by using anti-PARP12 and anti-FHL2 antibodies to perform endogenous Co-IP. As shown in Fig.?1d and Supplementary Physique?1, endogenous PARP12 and FHL2 formed a complex in all the examined cells. These results indicated that FHL2 was a partner of PARP12. Open in a separate window Fig. 1 PARP12 interacts with FHL2.a FHL2 was identified to be a PARP12-associated protein by affinity purification. Proteins identified in the PARP12 affinity purification complexes are listed with the number of unique peptides found and the coverage according to mass spectrometry analysis. b, c HA-FHL2 and SFB-PARP12 or GFP-PARP12 and SFB-FHL2 were co-transfected into HEK293T cells and applied to immunoprecipitation (IP) followed by Western blot using the indicated antibodies. Whole-cell lysates were blotted and shown as input. d Endogenous PARP12 interacts with FHL2. Lysates from HEK293T cells were subjected to IP and Western blot with the indicated antibodies. An irrelevant IgG was used as the negative control. *: non-specific bands FHL2 is not mono-ADP-ribosylated by PARP12 Considering that FHL2 interacts with PARP12 and that PARP12 is a mono-ADP-ribosyltransferase, we proposed that FHL2 was likely mono-ADP-ribosylated by PARP12. To test this hypothesis, we expressed and purified His-tagged PARP12 and GST-tagged FHL2 from and used these purified fusion proteins and biotinylated NAD+ to perform an in vitro mono-ADP-ribosylation assay. Western blot involving streptavidin-HRP revealed that His-PARP12 was mono-ADP-ribosylated by itself in the presence of biotinylated NAD+ (Fig.?2a). However, GST-FHL2 was not mono-ADP-ribosylated by His-PARP12 in the same reaction (Fig.?2a), suggesting that FHL2 was not the substrate of PARP12 in vitro. Anti-(ADP-ribose) antibody is specific to mono-ADP-ribose and can be used to detect mono-ADP-ribosylated polypeptides16. Hence, we performed an in vitro mono-ADP-ribosylation assay by using His-PARP12, GST-FHL2, and -NAD+. After the reaction occurred, the samples were analyzed through Western blot by using the anti-(ADP-ribose) antibody. In Fig.?2b, His-PARP12, not GST-FHL2, was.