Histone is the protein present in chromosomes.Unlike most proteins which have negative charge, histone is a protein having an overall positive charge.Histone carry positive charge because it has an abundance of basic proteins arginine and lysine.Histone
Positive charge on histone is also necessary for tight binding and coiling with the negatively charged DNA. Also, if you think about it, if histones were negatively charged, it would repel DNA instead of binding with it.