Genomes are spatially organized on many levels and the positioning of genes 
within the nucleus contributes to their proper expression. This positioning can 
also result in the clustering of genes with similar expression patterns, a 
phenomenon sometimes called "gene kissing." We have found that yeast genes are 
targeted to the nuclear periphery through interaction of the nuclear pore 
complex with small, cis-acting "DNA zip codes" in their promoters. Our recent 
study demonstrated that genes with the same zip codes cluster together at the 
nuclear periphery. The zip codes were necessary and sufficient to induce 
interchromosomal clustering. Finally, we identified a transcription factor 
(Put3) that binds to the GRS I zip code. Put3 binds to GRS I and is required for 
both GRS I-dependent positioning at the nuclear periphery and interchromosomal 
clustering of GRS I-targeted genes. We speculate that our findings might provide 
insight into other types of gene kissing, some of which also require cis-acting 
DNA sequences and trans-acting proteins.