Summary It is largely unclear whether genes that are naturally embedded in lamina-associated domains (LADs) are inactive due to their chromatin environment or whether LADs are merely secondary to the lack of transcription. We show that hundreds of human promoters become active when moved from their native LAD position to a neutral context in the same cells, indicating that LADs form a repressive environment. Another set of promoters inside LADs is able to “escape” repression, although their transcription elongation is attenuated. By inserting reporters into thousands of genomic locations, we demonstrate that escaper promoters are intrinsically less sensitive to LAD repression. This is not simply explained by promoter strength but by the interplay between promoter sequence and local chromatin features that vary strongly across LADs. Enhancers also differ in their sensitivity to LAD chromatin. This work provides a general framework for the systematic understanding of gene regulation by repressive chromatin.

Transcriptionally inactive genes are often positioned at the nuclear lamina (NL), as part of large lamina‐associated domains (LADs). Activation of such genes is often accompanied by repositioning toward the nuclear interior. How this process works and how it impacts flanking chromosomal regions are poorly understood. We addressed these questions by systematic activation or inactivation of individual genes, followed by detailed genome‐wide analysis of NL interactions, replication timing, and transcription patterns. Gene activation inside LADs typically causes NL detachment of the entire transcription unit, but rarely more than 50–100 kb of flanking DNA, even when multiple neighboring genes are activated. The degree of detachment depends on the expression level and the length of the activated gene. Loss of NL interactions coincides with a switch from late to early replication timing, but the latter can involve longer stretches of DNA. Inactivation of active genes can lead to increased NL contacts. These extensive datasets are a resource for the analysis of LAD rewiring by transcription and reveal a remarkable flexibility of interphase chromosomes.

Transcriptionally inactive genes are often positioned at the nuclear lamina (NL), as part of large lamina-associated domains (LADs). Activation of such genes is often accompanied by repositioning towards the nuclear interior. How this process works and how it impacts flanking chromosomal regions is poorly understood. We addressed these questions by systematic manipulation of gene activity and detailed analysis of NL interactions. Activation of genes inside LADs typically causes detachment of the entire transcription unit but rarely more than 50-100 kb of flanking DNA, even when multiple neighboring genes are activated. The degree of detachment depends on the expression level and the length of the activated gene. Loss of NL interactions coincides with a switch from late to early replication timing, but the latter can involve longer stretches of DNA. These findings show how NL interactions can be shaped locally by transcription and point to a remarkable flexibility of interphase chromosomes.

The present research examined two alternative interpretations of violation-of-expectation findings that young infants can represent hidden objects. One interpretation is that, when watching an event in which an object becomes hidden behind another object, infants form a prediction about the event's outcome while both objects are still visible, and then check whether this prediction was accurate. The other interpretation is that infants' initial representations of hidden objects are weak and short-lived and as such sufficient for success in most violation-of-expectation tasks (as objects are typically hidden for only a few seconds at a time), but not more challenging tasks. Five-monthold infants succeeded in reasoning about the interaction of a visible and a hidden object even though (1) the two objects were never simultaneously visible, and (2) a 3-or 4-min delay preceded the test trials. These results provide evidence for robust representations of hidden objects in young infants.

Chromatin accessibility complex/ATP-utilizing chromatin assembly and remodeling factor help to establish basal transcriptional repression, conceivably through improving the regular spacing of nucleosomes in euchromatin.

No abstract

DNA methylation controls gene expression, and once established, DNA methylation patterns are faithfully copied during DNA replication by the maintenance DNA methyltransferase Dnmt1. In vivo, Dnmt1 interacts with Uhrf1, which recognizes hemimethylated CpGs. Recently, we reported that Uhrf1‐catalyzed K18‐ and K23‐ubiquitinated histone H3 binds to the N‐terminal region (the replication focus targeting sequence, RFTS) of Dnmt1 to stimulate its methyltransferase activity. However, it is not yet fully understood how ubiquitinated histone H3 stimulates Dnmt1 activity. Here, we show that monoubiquitinated histone H3 stimulates Dnmt1 activity toward DNA with multiple hemimethylated CpGs but not toward DNA with only a single hemimethylated CpG, suggesting an influence of ubiquitination on the processivity of Dnmt1. The Dnmt1 activity stimulated by monoubiquitinated histone H3 was additively enhanced by the Uhrf1 SRA domain, which also binds to RFTS. Thus, Dnmt1 activity is regulated by catalysis (ubiquitination)‐dependent and ‐independent functions of Uhrf1.

BackgroundChromatin proteins control gene activity in a concerted manner. We developed a high-throughput assay to study the effects of the local chromatin environment on the regulatory activity of a protein of interest. The assay combines a previously reported multiplexing strategy based on barcoded randomly integrated reporters with Gal4-mediated tethering. We applied the assay to Drosophila heterochromatin protein 1a (HP1a), which is mostly known as a repressive protein but has also been linked to transcriptional activation.ResultsRecruitment to over 1000 genomic locations revealed that HP1a is a potent repressor able to silence even highly expressing reporter genes. However, the local chromatin context can modulate HP1a function. In pericentromeric regions, HP1a-induced repression was enhanced by twofold. In regions marked by a H3K36me3-rich chromatin signature, HP1a-dependent silencing was significantly decreased. We found no evidence for an activating function of HP1a in our experimental system. Furthermore, we did not observe stable transmission of repression over mitotic divisions after loss of targeted HP1a.ConclusionsThe multiplexed tethered reporter assay should be applicable to a large number of chromatin proteins and will be a useful tool to dissect combinatorial regulatory interactions in chromatin.Electronic supplementary materialThe online version of this article (doi:10.1186/s13072-016-0096-y) contains supplementary material, which is available to authorized users.