Question: Which post-translational histone modifications are characteristic of constitutive heterochromatin?

Context:
H3S10 phosphorylation marks constitutive heterochromatin during interphase in early mouse embryos until the 4-cell stage
We show here that the maternally inherited Snurf-Snrpn 3-Mb region, which is silenced by a potent transcription repressive mechanism, is uniformly enriched in histone methylation marks usually found in constitutive heterochromatin, such as H4K20me3, H3K9me3, and H3K79me3.
This result indicates that H3K36me3 is associated with both facultative and constitutive heterochromatin.
Classical histone modifications associated with heterochromatin, including H3K9me2, H3K27me1 and H3K27me2, were distributed throughout both A and B chromosomes.
In this review, available data will be evaluated concerning (1) the phylogenetic distribution of H3K9me as heterochromatin-specific histone modification and its evolutionary stability in relation to other epigenetic marks, (2) known families of H3K9 methyltransferases, (3) their responsibility for the formation of constitutive heterochromatin and (4) the evolution of Su(var)3-9-like and SUVH-like H3K9 methyltransferases
 While these regions were furthermore largely devoid of the constitutive heterochromatin marker H3K9-me3, we observed rapid and widespread deposition of H3K27-me3 across latent KSHV genomes, a bivalent modification which is able to repress transcription in spite of the simultaneous presence of activating marks.
Histone modifications in Arabidopsis- high methylation of H3 lysine 9 is dispensable for constitutive heterochromatin
The recent discovery of the first histone Lys methyltransferase has allowed the identification of a molecular mechanism in which the specific methylation of histone H3 at Lys9 generates a binding site for heterochromatin-associated proteins.
At the SUMO-1 labelled areas, the presence of HP1alpha protein, as well as of trimethylated H3-K9 and H4-K20 histone modifications, supports a role for SUMO-1 in constitutive heterochromatin organization.
Surprisingly, the marsupial Xi was stably enriched for modifications associated with constitutive heterochromatin in all eukaryotes (H4K20me3, H3K9me3).
Constitutive heterochromatin during mouse oogenesis: the pattern of histone H3 modifications and localization of HP1alpha and HP1beta proteins.
In fission yeast, heterochromatin formation requires RNAi and the histone H3K9 methyltransferase complex CLRC, composed of Clr4, Raf1, Raf2, Cul4, and Rik1. 
Methylation of histone H3 at lysine 9 (H3-Lys9) by site-specific histone methyltransferases (Suv39h HMTases) marks constitutive heterochromatin. 
H3S10 phosphorylation marks constitutive heterochromatin during interphase in early mouse embryos until the 4-cell stage.
In placental mammals non-coding XIST RNA triggers silencing of one X (Xi) and recruits a characteristic suite of epigenetic modifications, including the histone mark H3K27me3.

Answer: H3K9me3 is the major marker of constitutive heterochromatin. Other histone methylation marks usually found in constitutive heterochromatin, are H4K20me3 and H3K79me3. Classical histone modifications associated with heterochromatin include H3K9me2, H3K27me1 and H3K27me2. Histone H3 trimethylation at lysine 36 is associated with constitutive and facultative heterochromatin. H3S10 phosphorylation marks constitutive heterochromatin during interphase in early mouse embryos until the 4-cell stage
Exact answer: H3S10p, H3K36me3, H4K20me3, H3K9me3, H3K79me3, H3K9me2, H3K27me1, H3K27me2, H3K27me3