H1-0 and breast cancer: However, whereas the HBP1 transcription factor induced by retinoblastoma protein (RB) enhances the activity of histone H1.0 promoter in nuclear chromatin of murine erythroleukemia cells [57], and histone H1.0 is abundantly deposited in nucleolar chromatin of breast cancer cells [22], it is intriguing whether or not histone H1.0 activity is peculiarly linked to specialized cells affecting a specific processes, i.e. related to malignant transformation, or its accumulation is widespread across various cell types and necessary for maintaining a general cell processes.