POLR2K and Huntington disease: The set of HD-associated genes oscillating in SW620 cells included genes involved in cell death (CASP3, TP53, CYSC), mitochondrial oxidative phosphorylation (SOD2, SDHD, NDUFA2, NDUFA4, NDUFA4L2, NDUFAB1, NDUFS3, UQCR10, and UQCRHL), and gene transcription by RNA polymerase II (POLR2A, POLR2C, POLR2K, TAFA4, TBP, and TBPL1).