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34 pags., 8 figs. (+SI), The Akirin family of transcription cofactors are involved throughout the metazoan in the regulation of different biological processes (BPs) such as immunity, interdigital regression, muscle and neural development. Akirin do not have catalytic or DNA-binding capability and exert its regulatory function primarily through interacting proteins such as transcription factors, chromatin remodelers, and RNA-associated proteins. In the present study, we focused on the human Akirin2 regulome and interactome in neutrophil-like model human Caucasian promyelocytic leukemia HL60 cells. Our hypothesis is that metazoan evolved to have Akirin2 functional complements and different Akirin2-mediated mechanisms for the regulation of gene expression. To address this hypothesis, experiments were conducted using transcriptomics, proteomics and systems biology approaches in akirin2 knockdown and wildtype (WT) HL60 cells to characterize Akirin2 gene/protein targets, functional complements and to provide evidence of different mechanisms that may be involved in Akirin2-mediated regulation of gene expression. The results revealed Akirin2 gene/protein targets in multiple BPs with higher representation of immunity and identified immune response genes as candidate Akirin2 functional complements. In addition to linking chromatin remodelers with transcriptional activation, Akirin2 also interacts with histone H3.1 for regulation of gene expression., This work was supported by the Ministerio de Economıa, Industria y Competitividad (Spain) [grant number BFU2016-79892-P]; the Predoctoral Fellowship of the UCLM (to Sara Artigas-Jeronimo); the University of Castilla La Mancha, Spain (to Margarita ´ Villar); and the Fondo Europeo de Desarrollo Regional, FEDER, EU (to Margarita Villar).

This article belongs to the Collection New Frontiers in Tick Research., Ticks and tick-borne diseases (TBDs) represent a burden for human and animal health worldwide. Currently, vaccines constitute the safest and most effective approach to control ticks and TBDs. Subolesin (SUB) has been identified as a vaccine antigen for the control of tick infestations and pathogen infection and transmission. The characterization of the molecular function of SUB and the identification of tick proteins interacting with SUB may provide the basis for the discovery of novel antigens and for the rational design of novel anti-tick vaccines. In the present study, we used the yeast two-hybrid system (Y2H) as an unbiased approach to identify tick SUB-interacting proteins in an Ixodes ricinus cDNA library, and studied the possible role of SUB as a chromatin remodeler through direct interaction with histones. The Y2H screening identified Importin-α as a potential SUB-interacting protein, which was confirmed in vitro in a protein pull-down assay. The sub gene expression levels in tick midgut and fat body were significantly higher in unfed than fed female ticks, however, the importin-α expression levels did not vary between unfed and fed ticks but tended to be higher in the ovary when compared to those in other organs. The effect of importin-α RNAi was characterized in I. ricinus under artificial feeding conditions. Both sub and importin-α gene knockdown was observed in all tick tissues and, while tick weight was significantly lower in sub RNAi-treated ticks than in controls, importin-α RNAi did not affect tick feeding or oviposition, suggesting that SUB is able to exert its function in the absence of Importin-α. Furthermore, SUB was shown to physically interact with histone 4, which was corroborated by protein pull-down and western blot analysis. These results confirm that by interacting with numerous tick proteins, SUB is a key cofactor of the tick interactome and regulome. Further studies are needed to elucidate the nature of the SUB-Importin-α interaction and the biological processes and functional implications that this interaction may have., This research was supported by the Ministerio de Economía, Industria y Competitividad (Spain) grant BFU2016-79892-P and Laboratoire d’Excellence Integrative Biology of Emerging Infectious Diseases (France) grant ANR-10-LABX-62-IBEID. L.B.S. was funded by the United Kingdom Biotechnology and Biological Sciences Research Council grant number BB/P024270/1. S.A.-J. was supported by a predoctoral fellowship of the UCLM. M.V. was supported by the University of Castilla La Mancha, Spain and the Fondo Europeo de Desarrollo Regional, FEDER, EU.