SSX2IP promotes centrosome maturation and maintenance at the onset of vertebrate development, preserving centrosome integrity and mitosis during rapid cleavage divisions and in somatic cells.

Calmodulin (CaM) is a ubiquitous sensor/transducer of calcium signals in eukaryotic organisms. While CaM mediated calcium regulation of cytosolic processes is well established, there is growing evidence for the inclusion of organelles such as chloroplasts, mitochondria and peroxisomes into the calcium/calmodulin regulation network. A number of CaM-binding proteins have been identified in these organelles and processes such as protein import into chloroplasts and mitochondria have been shown to be governed by CaM regulation. What have been missing to date are the mediators of this regulation since no CaM or calmodulin-like protein (CML) has been identified in any of these organelles. Here we show that two Arabidopsis CMLs, AtCML3 and AtCML30, are localized in peroxisomes and mitochondria, respectively. AtCML3 is targeted via an unusual C-terminal PTS1-like tripeptide while AtCML30 utilizes an N-terminal, non-cleavable transit peptide. Both proteins possess the typical structure of CaMs, with two pairs of EF-hand motifs separated by a short linker domain. They furthermore display common characteristics, such as calcium-dependent alteration of gel mobility and calcium-dependent exposure of a hydrophobic surface. This indicates that they can function in a similar manner as canonical CaMs. The presence of close homologues to AtCML3 and AtCML30 in other plants further indicates that organellar targeting of these CMLs is not a specific feature of Arabidopsis. The identification of peroxisomal and mitochondrial CMLs is an important step in the understanding how these organelles are integrated into the cellular calcium/calmodulin signaling pathways.

Liver cancer represents the second most deadly human malignancy. The major histological subtype called hepatocellular carcinoma (HCC) arises by chronic inflammation‐triggered regenerative responses of normally quiescent hepatocytes and progenitors, respectively. Such regenerative stress accelerates the accumulation of genetic and epigenetic changes (Yamashita & Wang, ), while detailed mechanisms remain uncertain. In this issue of The EMBO Journal, Nikolaou et al present a novel HCC model that facilitates both isolation and molecular characterization of self‐renewing, HCC‐propagating cancer stem cells that could instruct future interventions (Nikolaou et al, ).

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