Chromosome-wide targeting mechanisms have until recently been consider only as a mechanism to equalize the transcriptional activity of the single male X-chromosome with that of the two female X-chromosomes, i.e., dosage compensation. Our discovery of the chromosome specific protein Painting of Fourth (POF) is the first example of a chromosome-wide targeting mechanism for an autosome. We have recently shown that POF and heterochromatin protein 1 (HP1) are involved in the global regulation of the 4th chromosome. POF binding is dependent on heterochromatin and POF and HP1 bind interdependently to the 4th chromosome. We have proposed a balancing mechanism involving POF and HP1 that provides a feed-back system for fine-tuning expression status of genes on the 4th chromosome. Balancing mechanisms may be a general way to regulate gene expression at a chromosome-wide level. The continued analysis of POF and chromosome-wide regulation focuses on three different questions: (1) Generality, function and mechanisms for chromosome targeting and regulation. (2) Establishment and propagation of chromatin structure within chromosomes. (3) Chromosome positioningin the nuclei. At present, POF is likely to represent the most compelling example of a chromosome targeting mechanism adapted for targeting of regulatory factors to an autosome. We believe that our work on POF has the potential to make major contribution to our understanding of chromosome-wide regulatory complexes, their composition, function and implication.