RNF144A and RNF144B: Important molecules for health.

Prognostic indicators of head and neck squamous cell carcinoma (HNSCC) were screened using molecular characterization databases, the TCGA dataset, and the GEO dataset, and the results revealed that RNF144A has significant prognostic value in HNSCC patients and that RNF144A is involved in signaling pathways of protein metabolism and ubiquitination [ 61 ]. RNF144A is frequently mutated or epigenetically silenced in cancers, providing a theoretical basis for assessing the loss of function of RNF144A in tumorigenesis [ 62 ]. Exposure of mice to oncogenic conditions after the knockdown of RNF144A resulted in an increased incidence of bladder cancer [ 62 ]. This is attributed to the fact that RNF144A interacts with PD-L1 in the cytoplasmic membrane and intracellular vesicles and promotes polyubiquitination and degradation of PD-L1, while knockdown of RNF144A can stabilize PD-L1 [ 62 ]. Varicella-associated kinase 3 (VRK3) is an ERK negative regulator that inhibits ERK-dependent apoptosis as a means of exerting cytoprotective effects [ 63 , 64 , 65 ]. It was found that RNF144A can interact with VRK3 to promote the ubiquitination degradation of VRK3, activate ERK, and promote apoptosis, and these effects are intensified under conditions of oxidative stress [ 63 ]. When cells were subjected to sustained or severe DNA damage, the expression of RNF144A was elevated in a p53-dependent manner, and RNF144A was found to interact with the catalytic subunits of DNA-dependent protein kinases (DNA-PKcs) in vivo and ex vivo to promote their ubiquitinated degradation [ 66 ]. This finding suggests that RNF144A may be involved in the p53-mediated apoptosis by downregulating DNA-PKcs [ 66 ]. It was reported that the histone deacetylase inhibitor TMU-35435 induced RNF144A to interact with DNA-PKcs, and RNF144A promoted the ubiquitination of DNA-PKcs as a combined treatment to induce apoptosis and autophagic cell death [ 67 ]. Epidermal growth factor receptor (EGFR) belongs to the family of receptor tyrosine kinases (PTKs) [ 68 ]. Ligands of EGFR, such as EGF and the transforming growth factor α, can initiate EGFR dimerization, ubiquitination, activation, and endocytosis upon binding to other ligands, and activation of the EGF/EGFR signaling pathway was found to result in cell migration, proliferation, and differentiation [ 69 , 70 ]. RNF144A and EGFR were reported to interact with each other to promote the ubiquitination of EGFR, maintain EGFR protein stabilization, and prolong EGF/EGFR signaling. Knockdown of RNF144A reduced the EGF-dependent cell proliferation [ 71 ]. A specific AluYd8 progenitor exists in the intron of the RNF144A gene, and 14 transcribed sequences are initiated in the opposite direction of the RNF144A gene, i.e., antisense transcripts, whose transcriptional activation may interfere with the transcription of the RNF144A gene or block the binding of the transcripts in the promoter [ 72 ]. The most common genetic mutation in human cancers is the p53 gene mutation [ 73 ]. Isolation and functional analysis of target genes showed that RNF144B is associated with cell cycle control, which is related to the regulation of p21WAF1/CIP1 by RNF144B. As a direct transcription target of p53, the products of p21WAF1 can inhibit cell proliferation by binding directly to the subunits of cell cycle protein-dependent kinase or E2F transcription factors or by inhibiting DNA replication through interaction with the proliferating cell nuclear antigen. RNF144B interacts with and promotes the ubiquitinated degradation of p21WAF1, and HCT116 cells with RNF144B overexpression can lead to decreased p21WAF1 protein expression when exposed to γ-rays. Inhibition of the RNF144B expression by antisense oligonucleotides was reported to lead to accumulation of the p21WAF1 protein [ 74 , 75 ]. It was found that RNF144B induces p53-dependent apoptosis through its C-terminal TCD structural domain, but not through the RING-IBR-RING structural domain, suggesting that this process is not related to the ubiquitination function of RNF144B [ 10 ]. In addition, p53-46F, a mutant type of p53, induced higher levels of RNF144B expression than the wild-type p53 [ 76 ]. p73 is a p53-related transcription factor belonging to the p53 transcription factor family, and TAp73 and ΔNp73 are two isoforms of p73 (the former pro-apoptotic and the latter inhibiting apoptosis) [ 77 , 78 , 79 ]. It was reported that TAp73 can induce RNF144B, which then promotes the ubiquitinated degradation of ΔNp73, and this differential regulation maintains the stability of TAp73 and ΔNp73 [ 80 ]. This finding provides a therapeutic pathway to enhance the chemosensitivity of tumor cells. Apoptin, which is a protein derived from the chicken anemia virus, can induce cell death in various cancer cells. More specifically, Apoptin induces the expression of TAp73 to result in apoptosis [ 81 ]. It was also found that Apoptin induces the expression of RNF144B, leading to degradation of ΔNp73 and activation of the pro-apoptotic target PUMA, which eventually results in cancer cell death [ 82 ].

RNF144A and RNF144B are “ancient” genes, first reported in 1982 [ 83 ], while they are also “time-honored” genes, which are now reported every year [ 24 , 46 ]. Their involvement in organ pathologies in almost every system ( Table 1 ) emphasizes their importance in human beings. Role and mechanism of RNF144A/RNF144B in different diseases By collating the literature on RNF144-related literature, we found that it is closely related to tumors. More noteworthy is the bidirectional role of RNF144 in tumors ( Table 2 , Figure 8 ). The tumor-promoting conditions and mechanisms are as follows: Formation of the RNF144A-ALK complex leads to RNF144A-promoted LUAD [ 22 ]. RNF144A promotes migration of M2 macrophages [ 25 ], and RNF144B promotes ubiquitinated degradation of pirh2 [ 26 ], which leads to RNF144 promoting gastric cancer. RNF144B promotes p21/p53 degradation in ovarian cancer [ 32 ]. RNF144B promotes phosphorylation of GSK3β in endometrial cancer [ 34 ]. RNF144B promotes ubiquitination degradation of NPM, which promotes leukemia [ 49 ]. RNF144B promotes MYC-driven lymphoma [ 50 ]. The tumor suppression and mechanism are as follows: RNF144B promotes the proliferation of tumor cells and also promotes the stabilization of tumor chromosomes, which leads to the suppression of LUAD by RNF144B [ 24 ]. RNF144A promotes the ubiquitination of DNA-PKcs and thereby inhibits HCC [ 29 ]. RNA144A promotes the degradation of LIN28B and thereby inhibits EOC [ 37 ]. RNF144A promotes ubiquitination degradation of YY1 [ 43 ], inhibits tumor cell proliferation and migration [ 44 ], and promotes ubiquitination degradation of HSPA2 [ 45 ], and these mechanisms lead to the inhibition of breast cancer by RNF144A. Dual role of RNF144 in tumors The dual roles of RNF144A/RNF144B in tumors. As a result, RNF144 promotes LUAD, gastric cancer, ovarian cancer, endometrial cancer, leukemia, and lymphoma and inhibits LUAD, HCC, ovarian cancer, and breast cancer. In addition, RNF144 is sometimes pro-carcinogenic and sometimes oncogenic in LUAD and ovarian cancer [ 22 , 23 , 24 ]. The mechanism underlying this phenomenon has been investigated to some extent, including gastric cancer, HCC, breast cancer, and leukemia, which are regulated by RNF144-mediated ubiquitination, and the degradation of p53 and LIN28B in ovarian cancer, which is also supposed to be RNF144-mediated ubiquitination, which needs to be further verified. In addition to being associated with tumors, RNF144A and RNF144B play important roles in neurological and infectious diseases. Most of the literature demonstrates that RNF144 has an anti-infective effect. When the organism is infected by viral DNA or Salmonella, RNF144 promotes STING activation or modulation of T-cell function and production of interferon, which enhances antiviral immunity [ 51 ]. When cells were stimulated by poly(I:C), RNF144 downregulated the release of pro-inflammatory cytokines by an unknown molecular mechanism [ 56 ]. Interestingly, RNF144 also had a bidirectional regulatory effect on cells after monocyte-macrophage induction by LPS. Zhang et al. demonstrated that after LPS induction in macrophages, RNF144 promoted ubiquitinated degradation of TBK1, leading to a decrease in interferon release and thus anti-inflammation [ 54 ]. Paradoxically, Ariffin et al. found that the release of IL-1β was reduced after LPS-induced RNF144B knockdown macrophages, while it increased after LPS-induced RNF144B overexpressing macrophages and thus pro-inflammatory [ 55 ]. This finding has not been verified in great detail, and its mechanism still needs to be further investigated. In neuropsychiatric disorders, RNF144 has consistent negative effects, promoting tumors, including gliomas and chordomas, or causing side effects from antipsychotics [ 15 , 18 , 19 , 20 , 21 ]. Considering the bidirectional regulatory role of RNF144 in other tumors and infectious diseases, it may have a similar role in other neurological disorders, and we can further investigate in this direction. In addition, we found that RNF144A and RNF144B, although both members of the RNF144 family, do not have identical regulatory roles in relation to disease pathways. In some diseases, they have opposite regulatory roles. For example, in LUAD, RNF144A promotes tumors while RNF144B inhibits them [ 22 , 23 , 24 ]. In certain diseases, they have coordinated and complementary roles. For example, in gastric cancer, RNF144A and RNF144B jointly promote tumor development by promoting M2 macrophage migration and ubiquitination degradation of pirh2, respectively [ 25 , 26 ]. This should be related to the difference in the number of amino acids or the different TM structural domains at the C-terminus. Unlike the bidirectional role of RNF144, other RBR E3s usually have a concerted role. For example, parkin, which has been shown to have a promoting effect in tumors such as HCC [ 84 , 85 ], drives apoptosis in HCC cells by inhibiting the NF-κB pathway by promoting the degradation of TRAF2 and TRAF6 [ 84 , 86 ]. HOIP is considered a protective factor for the organism. When HOIP is defective in the organism, it is more likely to acquire immunodeficiency [ 87 ]. This is because HOIP increases the ubiquitination of STAT1, which inhibits interferon production [ 88 ]. As ubiquitination-associated genes, RNF144A and RNF144B mostly regulate the activity of target proteins and signaling pathways by interacting with these proteins to promote their ubiquitination, mainly by facilitating the assembly of the K6-, K11-, K48-, and K63-linked ubiquitin chains [ 89 ]. However, the specific ubiquitination mechanisms of RNF144A and RNF144B in different diseases are currently understudied. There is only one adequate study reporting that RNF144A interacts with STING and promotes the ubiquitination of its K6 linkage at K236, which in turn induces downstream signaling molecules and protects against DNA viruses in inducing viral immunity [ 51 ]. Therefore, the mechanism underlying the ubiquitination modification of RNF144A still needs to be further explored, which also provides more research possibilities for developing novel disease-targeted therapies. Most of the experimental results in the current literature on RNF144 are based on in vitro models, with relatively few in vivo studies, so the conclusions available may be limited. More mice and human specimens will be needed in the future to verify the reliability of these experimental results. For now, RNF144 is involved in regulatory roles in numerous diseases, and exploring a criterion as a biomarker for diagnosing diseases, especially digestive and reproductive tumors, is worthy of our consideration, and the development of targeted biologics specific for RNF144 is a new direction for targeted therapy. However, as we mentioned earlier, RNF144 has bidirectional roles in tumors and inflammation, which makes it challenging to identify RNF144 as a criterion for disease diagnosis, and there is a long way to go to investigate new drugs targeting RNF144. We need to study the molecular mechanism of RNF144 regulation of diseases more profoundly to provide a reliable theoretical basis for diagnosis and targeted therapy.

Ubiquitination, a critical post-translational modification, regulates protein homeostasis through dynamic control of protein stability, subcellular localization, and functional activity [ 1 ]. Ubiquitination means the binding of ubiquitin molecules to target proteins via a cascade of enzymatic reactions induced by the ubiquitin-proteasome system [ 2 , 3 ]. Ubiquitination enzymes contain ubiquitin-activating enzymes (E1), ubiquitin-conjugating enzymes (E2), and ubiquitin-ligase enzymes (E3) [ 4 ]. E3 ligases are categorized into four mechanistically distinct classes based on their structural domains: Homologous to E6AP C-Terminus-type (HECT) containing a catalytic HECT domain; RING-type (Really Interesting New Gene) featuring RING finger domains mediating E2 interactions; RING-between-RING-type (RBR) employing a tripartite RING1-IBR-RING2 architecture; PCAF_N-type characterized by N-terminal p300/CBP-associated factor (PCAF) domains [ 5 , 6 ]. The RNF144 family proteins, comprising RNF144A and RNF144B (alternatively designated as PIR2, IBRDC2, and P53RFP), represent a distinct class of RBR E3 ubiquitin ligases. Structural analyses reveal a conserved bipartite architecture: an N-terminal RBR domain (RING1-IBR-RING2) and a C-terminal transmembrane (TM) domain ( Figure 1 ) [ 7 , 8 , 9 , 10 ]. Mechanistically, the RBR domain facilitates specific E2 ubiquitin-conjugating enzyme recruitment [ 11 ], while the TM domain exhibits dual functionality in membrane association and allosteric regulation of ligase activity [ 7 ]. Notably, emerging evidence indicates intrinsic functional significance of the TM domain beyond its structural role [ 12 ]. Despite growing recognition of RNF144 family involvement in diverse pathological conditions, systematic analyses of their disease-associated mechanisms remain conspicuously absent in current literature. We conducted a literature search in PubMed using the following query terms: “RNF144,” “RNF144A,” “RNF144B,” “PIR2,” “IBRDC2,” and “P53RFP” and ranging from 1982 to 2024. The result of search demonstrates the literatures about RNF144 family proteins were concentrating on recently 10 years. This review comprehensively examines regulatory mechanisms and therapeutic implications of RNF144. Schematic structure of RNF144A/RNF144B.