Component of E3 ubiquitin ligase SCF complexes, which mediate the ubiquitination and subsequent proteasomal degradation of target proteins. Seems to recruit the E2 ubiquitination enzyme, like UBC3/CDC34, to the complex and brings it into close proximity to the substrate. Component of the rik1-associated E3 ubiquitin ligase complex that shows ubiquitin ligase activity and is required for histone H3K9 methylation. H3K9me represents a specific tag for epigenetic transcriptional repression by recruiting swi6/HP1 to methylated histones which leads to transcriptional silencing within centromeric heterochromatin, telomeric regions and at the silent mating-type loci. Protein modification; protein ubiquitination. Part of a SCF E3 ubiquitin ligase complex containing psh1, pip1, pcul1 and the F-box proteins pop1 and pop2. Instead of the pop1/pop2 heterodimer also homooligomers of pop1 or pop2 may be present in the complex. Component of the rik1-associated E3 ubiquitin ligase complex composed of at least clr4, cul4, pip1, raf1 and raf2. Interacts with cul3. The RING-type zinc finger domain is essential for ubiquitin ligase activity. It coordinates an additional third zinc ion.