Hi-C and chromatin immunoprecipitation (ChIP) have been combined to identify long-range chromatin interactions genome-wide at reduced cost and enhanced resolution, but extracting information from the resulting datasets has been challenging. Here we describe a computational method, MAPS, Model-based Analysis of PLAC-seq and HiChIP, to process the data from such experiments and identify long-range chromatin interactions. MAPS adopts a zero-truncated Poisson regression framework to explicitly remove systematic biases in the PLAC-seq and HiChIP datasets, and then uses the normalized chromatin contact frequencies to identify significant chromatin interactions anchored at genomic regions bound by the protein of interest. MAPS shows superior performance over existing software tools in the analysis of chromatin interactions from multiple PLAC-seq and HiChIP datasets centered on different transcriptional factors and histone marks. MAPS is freely available at https://github.com/ijuric/MAPS.

MOTIVATION: ChIP-Seq is the standard method to identify genome-wide DNA-binding sites for transcription factors (TFs) and histone modifications. There is a growing need to analyze experiments with biological replicates, especially for epigenomic experiments where variation among biological samples can be substantial. However, tools that can perform group comparisons are currently lacking. RESULTS: We present a peak-calling prioritization pipeline (PePr) for identifying consistent or differential binding sites in ChIP-Seq experiments with biological replicates. PePr models read counts across the genome among biological samples with a negative binomial distribution and uses a local variance estimation method, ranking consistent or differential binding sites more favorably than sites with greater variability. We compared PePr with commonly used and recently proposed approaches on eight TF datasets and show that PePr uniquely identifies consistent regions with enriched read counts, high motif occurrence rate and known characteristics of TF binding based on visual inspection. For histone modification data with broadly enriched regions, PePr identified differential regions that are consistent within groups and outperformed other methods in scaling False Discovery Rate (FDR) analysis. AVAILABILITY AND IMPLEMENTATION: http://code.google.com/p/pepr-chip-seq/.

IP routing lookup schemes using single-step TCAM used in core routers demand entries being sorted according to prefix lengths in descending order relative to TCAM addresses. The sorting operations related to addresses have disadvantageous affections to the entry updating speed and lookup continuity. This paper provides a novel IPv4/IPv6 dual-stack routing lookup method based on BSPL (bi-search on prefix length), which using multi-step TCAM pipelining based on bi-search on prefix length. Its outstanding advantages include that no entry sorting is needed, lookup speed is high, entry updating is completed fast with pipelining, and lookup continuity is enhanced. It satisfies wire-speed (48B-packet) forwarding of OC-768 (40Gbps) interfaces of IPv4/IPv6 dual-stack core routers.