Polo-like kinase 4 (PLK4) is a major player in centriole biogenesis: in its absence centrioles fail to form, while in excess leads to centriole amplification. The SCF-Slimb/βTrCP-E3 ubiquitin ligase controls PLK4 levels through recognition of a conserved phosphodegron. SCF-Slimb/βTrCP substrate binding and targeting for degradation is normally regulated by phosphorylation cascades, controlling complex processes, such as circadian clocks and morphogenesis. Here, we show that PLK4 is a suicide kinase, autophosphorylating in residues that are critical for SCF-Slimb/βTrCP binding. We demonstrate a multisite trans-autophosphorylation mechanism, likely to ensure that both a threshold of PLK4 concentration is attained and a sequence of events is observed before PLK4 can autodestruct. First, we show that PLK4 trans-autophosphorylates other PLK4 molecules on both Ser293 and Thr297 within the degron and that these residues contribute differently for PLK4 degradation, the first being critical and the second maximizing auto-destruction. Second, PLK4 trans-autophosphorylates a phospho-cluster outside the degron, which regulates Thr297 phosphorylation, PLK4 degradation, and centriole number. Finally, we show the importance of PLK4-Slimb/βTrCP regulation as it operates in both soma and germline. As βTrCP, PLK4, and centriole number are deregulated in several cancers, our work provides novel links between centriole number control and tumorigenesis.

Highlights d Single-cell RNA-seq reveals differential tissue-specific adaptation of Vg6 + T cells d Skin Vg6 + T cells show an activated IL-17-and amphiregulinproducing effector phenotype d Expression of Bcl2a1 family proteins protect activated skin Vg6 + T cells from apoptosis d Skin Vg6 + and Vg4 + T cells can be distinguished by Scart1 versus Scart2 expression

Cilia and flagella are involved in a variety of processes and human diseases, including ciliopathies and sterility. Their motility is often controlled by a central microtubule (MT) pair localized within the ciliary MT-based skeleton, the axoneme. We characterized the formation of the motility apparatus in detail in Drosophila spermatogenesis. We show that assembly of the central MT pair starts prior to the meiotic divisions, with nucleation of a singlet MT within the basal body of a small cilium, and that the second MT of the pair only assembles much later, upon flagella formation. BLD10/CEP135, a conserved player in centriole and flagella biogenesis, can bind and stabilize MTs and is required for the early steps of central MT pair formation. This work describes a genetically tractable system to study motile cilia formation and provides an explanation for BLD10/CEP135's role in assembling highly stable MT-based structures, such as motile axonemes and centrioles.

microRNA (miRNA) mediated regulation of protein expression has emerged as an important mechanism in T-cell physiology, from development and survival to activation, proliferation, and differentiation. One of the major classes of proteins involved in these processes are cytokines, which are both key input signals and major products of T-cell function. Here, we summarize the current data on the molecular cross-talk between cytokines and miRNAs: how cytokines regulate miRNA expression, and how specific miRNAs control cytokine production in T cells. We also describe the inflammatory consequences of deregulating the miRNA/cytokine axis in mice and humans. We believe this topical area will have key implications for immune modulation and treatment of autoimmune pathology. Keywords:Cytokines r Inflammation r miRNA r T cells microRNAs as regulators of protein expressionBiological processes require the integration of environmental stimuli at the level of gene expression. The robustness of genetic networks depends on the distinction between physiological responses (to particular cues) and biological "noise" (stochastic variations), which can be achieved, for example, by establishing feed-forward transcriptional loops. Over the past two decades, a new mechanism that interacts with transcriptional loops and sets additional thresholds, which enable cells to filter physiological signals from noise has emerged; this mechanism regulates gene expression at the posttranscriptional level and relies on microRNAs (miRNAs; reviewed in [1]). These are an abundant class of evolutionarily conserved small noncoding (untranslated) RNA species that control target mRNA stability, degradation, and translation, thus affecting the majority of mammalian genes [2].Correspondence: Dr. Anita Q. Gomes e-mail: anitagomes@medicina.ulisboa.ptIn the conventional miRNA biogenesis pathway, RNA polymerase II transcribed pri-miRNAs are processed by the nuclear RNase III enzyme Drosha (complexed with DGCR8) to generate 60-70 nt stem-loop intermediates, the pre-miRNAs, that are further processed into 19-24mers in the cytoplasm by another key RNase III, Dicer. Mature miRNAs are then incorporated into RNAinduced silencing complexes, whose core components are proteins of the Argonaute family (Ago1-4), which use the 5 end (nucleotides 2-8) "seed sequence" of the miRNA to recognize complementary mRNA transcripts (mostly in their 3 untranslated region) for deadenylation or inhibition of translation, ultimately resulting in mRNA decapping and decay (reviewed in [3,4]).Unique spatial and temporal expression patterns in distinct hematopoietic cell lineages are suggestive of multiple roles for miRNAs in hematopoiesis, self-tolerance, and in immune responses, which have been explored over the past decade (reviewed in [5,6]). Over a 100 different miRNAs have been shown to be expressed by cells of the immune system, where * These authors contributed equally to this work as first authors. * * These authors contributed equally to this work as last authors.C 2015 WILEY-VCH Ve...