Adrenalectomy facilitates ATAT1 expression and α-tubulin acetylation in ACTH-producing corticotrophs

Mitotic Acetylation of Microtubules Promotes Centrosomal PLK1 Recruitment and Is Required to Maintain Bipolar Spindle Homeostasis

Tubulin post-translational modifications regulate microtubule properties and functions. Mitotic spindle microtubules are highly modified. While tubulin detyrosination promotes proper mitotic progression by recruiting specific microtubule-associated proteins motors, tubulin acetylation that occurs on specific microtubule subsets during mitosis is less well understood. Here, we show that siRNA-mediated depletion of the tubulin acetyltransferase ATAT1 in epithelial cells leads to a prolonged prometaphase arrest and the formation of monopolar spindles. This results from collapse of bipolar spindles, as previously described in cells deficient for the mitotic kinase PLK1. ATAT1-depleted mitotic cells have defective recruitment of PLK1 to centrosomes, defects in centrosome maturation and thus microtubule nucleation, as well as labile microtubule-kinetochore attachments. Spindle bipolarity could be restored, in the absence of ATAT1, by stabilizing microtubule plus-ends or by increasing PLK1 activity at centrosomes, demonstrating that the phenotype is not just a consequence of lack of K-fiber stability. We propose that microtubule acetylation of K-fibers is required for a recently evidenced cross talk between centrosomes and kinetochores.

Sperm-borne miR-202 targets SEPT7 and regulates first cleavage of bovine embryos via cytoskeletal remodeling

In mammals, sperm-borne regulators can be transferred to oocytes during fertilization and have different effects on the formation of pronuclei, the first cleavage of zygotes, the development of preimplantation embryos and even the metabolism of individuals after birth. The regulatory role of sperm microRNAs (miRNAs) in the development of bovine preimplantation embryos has not been reported in detail. By constructing and screening miRNA expression libraries, we found that miR-202 was highly enriched in bovine sperm. As a target gene of miR-202, co-injection of SEPT7 siRNA can partially reverse the accelerated first cleavage of bovine embryos caused by miR-202 inhibitor. In addition, both a miR-202 mimic and SEPT7 siRNA delayed the first cleavage of somatic cell nuclear transfer (SCNT) embryos, suggesting that miR-202-SEPT7 mediates the delay of first cleavage of bovine embryos. By further exploring the relationship between miR-202/SEPT7, HDAC6 and acetylated α-tubulin during embryonic development, we investigated how sperm-borne miR-202 regulates the first cleavage process of bovine embryos by SEPT7 and demonstrate the potential of sperm-borne miRNAs to improve the efficiency of SCNT.

Protein acetylation and deacetylation: An important regulatory modification in gene transcription (Review)

Cells primarily rely on proteins to perform the majority of their physiological functions, and the function of proteins is regulated by post-translational modifications (PTMs). The acetylation of proteins is a dynamic and highly specific PTM, which has an important influence on the functions of proteins, such as gene transcription and signal transduction. The acetylation of proteins is primarily dependent on lysine acetyltransferases and lysine deacetylases. In recent years, due to the widespread use of mass spectrometry and the emergence of new technologies, such as protein chips, studies on protein acetylation have been further developed. Compared with histone acetylation, acetylation of non-histone proteins has gradually become the focus of research due to its important regulatory mechanisms and wide range of applications. The discovery of specific protein acetylation sites using bioinformatic tools can greatly aid the understanding of the underlying mechanisms of protein acetylation involved in related physiological and pathological processes.

ATAT1 is essential for regulation of homeostasis-retaining cellular responses in corticotrophs along hypothalamic-pituitary-adrenal axis

The production and secretion of adrenocorticotropin, a proopiomelanocortin (POMC)-derived hormone, by corticotrophs in the anterior pituitary, is regulated by corticotrophin-releasing hormone (CRH) and glucocorticoids. We have previously demonstrated that adrenalectomy induces α-tubulin N-acetyltransferase 1 (ATAT1) expression and α-tubulin acetylation in corticotrophs. However, the regulatory mechanism of ATAT1 expression and the function of acetylated microtubules in corticotrophs are unclear. Here, we analyze the effect of CRH or dexamethasone on Atat1 expression in the mouse corticotroph AtT20 cell line. The expression of Atat1 was increased by CRH and decreased by dexamethasone in AtT20 cells. We examined the effect of Atat1 knockdown on the expression of POMC-associated genes and the dexamethasone-induced nuclear translocation of glucocorticoid receptor (GR) by real-time polymerase chain reaction and Western blot analysis, respectively. Atat1 knockdown resulted in a significant increase in the expression of ACTH-producing genes and decreased the dexamethasone-induced nuclear translocation of GR accompanied with a reduction in α-tubulin acetylation. Atat1 overexpression resulted in a significant increase in α-tubulin acetylation and the dexamethasone-induced nuclear translocation of GR. These results suggest that the acetylated microtubules function as the rail-line for the transportation of GR into the nucleus. We conclude that ATAT1 finely tunes the cellular responses of corticotrophs to hormonal stimulation through an intracellular feedback circuit.