Transcription factor GATA4 drives RNA polymerase III-directed transcription and transformed cell proliferation through a filamin A/GATA4/SP1 pathway

The Role of tRNA-Centered Translational Regulatory Mechanisms in Cancer

Cancer is a leading cause of morbidity and mortality worldwide. While numerous factors have been identified as contributing to the development of malignancy, our understanding of the mechanisms involved remains limited. Early cancer detection and the development of effective treatments are therefore critical areas of research. One class of molecules that play a crucial role in the transmission of genetic information are transfer RNAs (tRNAs), which are the most abundant RNA molecules in the human transcriptome. Dysregulated synthesis of tRNAs directly results in translation disorders and diseases, including cancer. Moreover, various types of tRNA modifications and the enzymes responsible for these modifications have been implicated in tumor biology. Furthermore, alterations in tRNA modification can impact tRNA stability, and impaired stability can prompt the cleavage of tRNAs into smaller fragments known as tRNA fragments (tRFs). Initially believed to be random byproducts lacking any physiological function, tRFs have now been redefined as non-coding RNA molecules with distinct roles in regulating RNA stability, translation, target gene expression, and other biological processes. In this review, we present recent findings on translational regulatory models centered around tRNAs in tumors, providing a deeper understanding of tumorigenesis and suggesting new directions for cancer treatment.

STAT3 potentiates RNA polymerase I-directed transcription and tumor growth by activating RPA34 expression

BACKGROUND

Deregulation of either RNA polymerase I (Pol I)-directed transcription or expression of signal transducer and activator of transcription 3 (STAT3) correlates closely with tumorigenesis. However, the connection between STAT3 and Pol I-directed transcription hasn't been investigated.

METHODS

The role of STAT3 in Pol I-directed transcription was determined using combined techniques. The regulation of tumor cell growth mediated by STAT3 and Pol I products was analyzed in vitro and in vivo. RNAseq, ChIP assays and rescue assays were used to uncover the mechanism of Pol I transcription mediated by STAT3.

RESULTS

STAT3 expression positively correlates with Pol I product levels and cancer cell growth. The inhibition of STAT3 or Pol I products suppresses cell growth. Mechanistically, STAT3 activates Pol I-directed transcription by enhancing the recruitment of the Pol I transcription machinery to the rDNA promoter. STAT3 directly activates Rpa34 gene transcription by binding to the RPA34 promoter, which enhances the occupancies of the Pol II transcription machinery factors at this promoter. Cancer patients with RPA34 high expression lead to poor survival probability and short survival time.

CONCLUSION

STAT3 potentiates Pol I-dependent transcription and tumor cell growth by activating RPA34 in vitro and in vivo.

STAT3 promotes RNA polymerase III-directed transcription by controlling the miR-106a-5p/TP73 axis

Deregulation of Pol III products causes a range of diseases, including neural diseases and cancers. However, the factors and mechanisms that modulate Pol III-directed transcription remain to be found, although massive advances have been achieved. Here, we show that STAT3 positively regulates the activities of Pol III-dependent transcription and cancer cell growth. RNA-seq analysis revealed that STAT3 inhibits the expression of TP73, a member of the p53 family. We found that TP73 is not only required for the regulation of Pol III-directed transcription mediated by STAT3 but also independently suppresses the synthesis of Pol III products. Mechanistically, TP73 can disrupt the assembly of TFIIIB subunits and inhibit their occupancies at Pol III target loci by interacting with TFIIIB subunit TBP. MiR-106a-5p can activate Pol III-directed transcription by targeting the TP73 mRNA 3' UTR to reduce TP 73 expression. We show that STAT3 activates the expression of miR-106a-5p by binding to the miRNA promoter, indicating that the miR-106a-5p links STAT3 with TP73 to regulate Pol III-directed transcription. Collectively, these findings indicate that STAT3 functions as a positive regulator in Pol III-directed transcription by controlling the miR-106a-5p/TP73 axis.

GATA-binding protein 4 promotes neuroinflammation and cognitive impairment in Aβ1-42 fibril-infused rats through small nucleolar RNA host gene 1/miR-361-3p axis

Aging with dysregulated metabolic and immune homeostasis stimulates pyroptosis, neuroinflammation, and cellular senescence, thus contributing to etiopathogenesis of Alzheimer's disease. GATA-binding protein 4 (GATA4) functions as a transcriptional factor in response to DNA damage, and is associated with neuroinflammation and cellular senescence. The role of GATA4 in Alzheimer's disease was investigated. GATA4 was elevated in hippocampus of Aβ_1-42 fibril-infused rats. Injection with shRNA targeting GATA4 reduced escape latency with increase of time in target quadrant and number of platform crossings in Aβ_1-42 fibril-infused rats. Moreover, knockdown of GATA4 ameliorated morphological changes of hippocampus and reduced amyloid plaque deposition in Aβ_1-42 fibril-infused rats. Silence of GATA4 repressed neuroinflammation and apoptosis in Aβ_1-42 fibril-infused rats. Loss of GATA4 in Aβ_1-42 fibril-infused rats reduced the expression of specificity protein 1 (Sp1) to downregulate long noncoding RNA small nucleolar RNA host gene 1 (SNHG1) and upregulated miR-361-3p. Loss of SNHG1 ameliorated learning and memory impairments in Aβ_1-42 fibril-infused rats. Overexpression of Sp1 attenuated GATA4 silence-induced decrease of escape latency, increase of time in target quadrant, and number of platform crossings in Aβ_1-42 fibril-infused rats. In conclusion, silence of GATA4 ameliorated cognitive dysfunction and inhibited hippocampal inflammation and cell apoptosis through regulation of Sp1/SNHG1/miR-361-3p.