Zinc finger (ZnF) domains are present in at least 5% of human proteins. First characterized as binding to DNA, ZnFs display extraordinary binding plasticity and can bind to RNA, lipids, proteins, and protein post-translational modifications (PTMs). The diverse binding properties of ZnFs have made their functional characterization challenging. While once confined to large and poorly characterized protein families, proteomic, cellular, and molecular studies have begun to shed light on their involvement as protectors of the genome. We focus here on the emergent roles of ZnF domain-containing proteins in promoting genome integrity, including their involvement in telomere maintenance and DNA repair. These findings have highlighted the need for further characterization of ZnF proteins, which can reveal the functions of this large gene class in normal cell function and human diseases, including those involving genome instability such as aging and cancer.

For most reef-building corals, the establishment of symbiosis occurs via horizontal transmission, where juvenile coral recruits acquire their algal symbionts (family Symbiodiniaceae) from their surrounding environment post-settlement. This transmission strategy allows corals to interact with a diverse array of symbionts, potentially facilitating adaptation to the newly settled environment. We exposed aposymbiotic Pseudodiploria strigosa recruits from the Flower Garden Banks to natal reef sediment (C-S+), symbiotic adult coral fragments (C+S-), sediment and coral fragments (C+S+), or seawater controls (C-S-) and quantified rates of symbiont uptake and Symbiodiniaceae community composition within each recruit using metabarcoding of the ITS2 locus. The most rapid uptake was observed in C+S+ treatments and this combination also led to the highest symbiont alpha diversity in recruits. While C-S+ treatments exhibited the next highest uptake rate, only one individual recruit successfully established symbiosis in the C+S-treatment, suggesting that sediment both serves as a direct symbiont source for coral recruits and promotes (or, potentially, mediates) transmission from adult coral colonies. In turn, presence of adult corals facilitated uptake from the sediment, perhaps via chemical signaling. Taken together, our results reinforce the key role of sediment in algal symbiont uptake by P. strigosa recruits and suggest that sediment plays a necessary, but perhaps not sufficient, role in the life cycle of the algal Symbiodinaceae symbionts.

Histone H2A variants play important roles in maintaining the integrity of the genome. For example, the histone variant H2AX is phosphorylated on Ser139 (called γH2AX) at DNA double-strand breaks (DSB) and serves as a signal for the initiation of downstream DNA damage response (DDR) factor recruitment and DNA repair activities within damaged chromatin. For decades, genetic studies in human cells involving DNA damage signaling and repair factors have relied mostly on either knockdown by RNA interference (i.e., shRNA and siRNA) or the use of mouse embryonic fibroblasts derived from knockout (KO) mice. Recent advances in gene editing using ZNF nuclease, TALEN, and CRISPR/Cas9 have allowed the generation of human KO cell lines, allowing genetic models for studying the DDR, including histone H2A variants in human cells. Here, we describe a detailed protocol for generating and verifying KO of H2AX and macroH2A histone H2A variants using CRISPR/Cas9 gene editing in human cancer cell lines. This protocol allows the use and development of genetic systems in human cells to study histone variants and their functions, including within the DDR.

19For most reef-building corals, the establishment of symbiosis occurs via horizontal 20 transmission, where juvenile coral recruits acquire their algal symbionts (family Symbiodiniaceae) 21 from their surrounding environment post-settlement. This transmission strategy allows corals to 22 interact with a diverse array of symbionts, potentially facilitating adaptation to the newly settled 23 environment. We exposed aposymbiotic Pseudodiploria strigosa recruits from the Flower Garden 24Banks to natal reef sediment (C-S+), symbiotic adult coral fragments (C+S-), sediment and coral 25 fragments (C+S+), or seawater controls (C-S-) and quantified rates of symbiont uptake and 26Symbiodiniaceae community composition within each recruit using metabarcoding of the ITS2 27 locus. The most rapid uptake was observed in C+S+ treatments and this combination also led to 28 the highest symbiont alpha diversity in recruits. While C-S+ treatments exhibited the next highest 29 uptake rate, only one individual recruit successfully established symbiosis in the C+S-treatment, 30suggesting that sediment both serves as a direct symbiont source for coral recruits and promotes 31 (or, potentially, mediates) transmission from adult coral colonies. In turn, presence of adult corals 32 facilitated uptake from the sediment, perhaps via chemical signaling. Taken together, our results 33 reinforce the key role of sediment in algal symbiont uptake by P. strigosa recruits and suggest that 34 sediment plays a necessary, but perhaps not sufficient, role in the life cycle of the algal 35Symbiodinaceae symbionts. 36 37